What explanations have scholars proposed for the rejection of the Didache from the Canon?

The *[Didache](https://en.wikipedia.org/wiki/Didache)* ([full text](http://www.catholicplanet.com/ebooks/didache.htm)) is an early Christian document giving advice on various "practical matters" such as how to baptize, when to fast, how to celebrate the Lord's Supper, etc. It's hard to date, but generally scholars think it was contemporary with at least parts of the NT. And it claimed apostolic authority. Although the *Didache* enjoyed high status in the second-century church, the document ultimately did not make the Canon of the New Testament. There doesn't seem to be a documented reason for the exclusion in the writings of the Church Fathers, so I imagine it is mostly speculation on what caused its decline in popularity and ultimate failure to make the canon. Nonetheless, what reasons have scholars cited as possible reasons for its exclusion? (Although I do consider "the Holy Spirit didn't guide believers to preserve it" a valid reason for exclusion, that isn't what I am looking for here.)