Why are non-Catholics prohibited from taking the eucharist?

This is a question I've often had, why exactly a non-Catholic is prohibited from taking the eucharist , if they believe the correct things about the eucharist, and are following Jesus teachings. Whenever I've found an answer, normally it is that Protestants and other non-Catholics who are not in communion with the Catholic church (some orthodox excluded) would bring harm upon themselves because they don't recognize Christ's presence in the eucharist, i.e. transubstantiation, even though logic of transubstantiation was not formalized until the 11th century. However, there are a couple of problems with this answer. First, anywhere from 1/3 to 2/3 of US Catholics believe the eucharist is just a symbol . Yet, if 1/3 of the congregation suddenly dropped dead from taking the eucharist unworthily, as Paul warns, I'm sure it'd be noticeable. Nor are any of them holding back. While a Catholic service for other nationalities tends to have many holding back, US Catholics are not shy at all about lining up to receive the eucharist. Nor are the confession rates very high (less than 1/2 just once a year), so odds are very high that a US Catholic is taking the the eucharist both with the wrong understanding and wrong moral disposition. So, there doesn't seem to be a lack of opportunity for US Catholics to keel over en masse from taking the eucharist unworthily. However, as far as I'm aware, there is no evidence this is happening. Thus, taking the eucharist unworthily seems more a theoretical concern than a realistic concern, at least as far as physical well being goes. Perhaps only spiritual well being is the concern, but this is not what Paul warns about in 1 Corinthians 11:29-30, he specifically mentions people becoming physically sick and dying from taking the eucharist unworthily. > For those who eat and drink without discerning the body of Christ eat and drink judgment on themselves. That is why many among you are weak and sick, and a number of you have fallen asleep. Spiritual harm is pretty hard to know evidentially if there is no physical consequences. However, accepting that taking the eucharist unworthily spiritually kills someone, without physical effect, this would only be a problem for those spiritually alive. Yet those outside the Catholic church are either already spiritually dead (how can you kill a dead thing?), or they are an "ecclesiastical community" and spiritually alive. And if they are considered spiritually alive, believe in the real presence, and are morally disposed, then how would taking the eucharist be of spiritual harm? Which brings me to the next point. There are a number of other non-Catholics who do recognize the real presence in one way or another, but are also denied communion: some Orthodox, ancient churches considered heretical by Catholics, Anglicans, Lutherans, Calvinists, some non-denominational Christians, etc. Yet, all of these are barred from taking the eucharist, even though they are observing Paul's warning. Maybe because they don't believe the precise correct thing about the confection of the eucharist, that it has to be done by a priest with a valid ordination coming down from the pope, then that causes some kind of problem. Maybe they have a Protestant priesthood of believers perspective, or don't believe in papal supremacy. But, this makes taking the eucharist worthily dependent on doctrines that weren't officially declared until centuries after Christ came to earth. What happened to everyone before transubstantiation and papal supremacy were defined? Another weird thing about this line of thought is that the priest could be a complete atheist and moral reprobate, and still validly confect the eucharist, yet for someone to take the eucharist worthily requires correct belief about a host of tricky theological subjects and be in a state of grace. Another answer I've heard is that taking the eucharist is a communal activity, and so groups not part of the Catholic community shouldn't take the eucharist. However, there are many non-Catholics that are very dedicated to the cause of Christ. For instance, evangelical Protestants, Mormons and Jehovah's Witnesses in the US are [much more likely] to follow Catholic moral teachings on abortion than a US Catholic. The orthodox believe in all the same essentials as Catholics, except for papal primacy, although they believe the pope is the "first among equals". Yet only a portion of the orthodox church is allowed to take the eucharist at a Catholic church. Conversely, a significant chunk of US Catholics that take communion don't believe in following church authority, seemingly at all, as mentioned above. Yet, there is never much concern about them taking the eucharist. Very occasionally will a public personality be barred, who has publicly stated they hold to a position clearly at odds with Catholic teaching, such as abortion, but such barring of any Catholic almost never happens. So, it is unclear exactly what being part of the Catholic community means that is relevant for taking the eucharist. A potential aspect to the answer I want to distinguish. There is the canon law aspect, where it is clear that taking the eucharist is prohibited for all non-Catholics unless there is a special declared exception. So, an [answer stating "the canon law says so"] is not quite what I'm looking for. Rather, I'm trying understand a more fundamental aspect, which is the "wherefore". It doesn't appear concern for physical well being is a realistic concern, as explained above from lack of evidence that physical harm is caused. Spiritual well being could be an answer, since there doesn't need to be tangible evidence of harm, but this is an answer that is hard for me to understand the logical consistency. Nor does the communal aspect make a lot of sense, since the Catholic position bars many who are in line with Catholic moral law and Christ's mission, and accepts many who are not. So, if someone knows a "wherefore" that avoids the sorts of answers I have already covered, or at least clears up my misunderstandings, I would be quite interested to hear. UPDATE: I'm wrong about the Orthodox. Looks like they are all allowed , at least by the Catholic church but maybe not from their side, to received eucharist at a Catholic church. UPDATE 2: Another sort of answer that I think misses the mark is one to the effect of "allowing non-Catholics to take the eucharist gives a false impression of unity". The problem with this sort of answer is that it is barring the eucharist based on symbolism, instead of something that actually happens to the people taking the eucharist. If the person is correctly disposed to take the eucharist, i.e. believes it is truly the body, blood, soul and divinity of Jesus and is in a state of grace after confession, then the eucharist should be efficacious. Jesus says the eucharist is a life saving medicine, i.e. gives people eternal life. So, whatever symbolism of the act that would be secondary to the life saving effect of the eucharist, just like a US field hospital would give life saving treatment to a captured enemy combatant. Ironically, this symbolism based reasoning is similar to the Zwinglian perspective that the eucharist is just a symbol, so it is strange for that to be a Catholic rationale. Conversely, as mentioned, many Catholics take the eucharist who don't recognize church authority or perhaps even Christ, just out of cultural or social conformity, and are thus more out of unity with the church than a true believer who is not Catholic. Yet, there is no effort whatsoever to remedy this actual lack of unity, and only effort to remedy the symbolic lack of unity.