Why does Ash Wednesday not appear in the list of holy days of obligation?

I was surprised to learn that Ash Wednesday is not one of the Catholic Holy Days of Obligation (see [this list](https://www.omvusa.org/blog/catholic-holy-days-of-obligation/)) although it is listed [here](https://hallow.com/blog/holy-days-of-obligation/) as "important liturgical observances". I thought Catholics are obliged to go to Mass on Ash Wednesday, or do they just need to fast ([according to precept #4](http://www.stvincentschurch.com/uploads/4/2/5/8/42588219/the_precepts_of_the_catholi_church.pdf) because precept #1 says to "... attend Mass and holy days of obligation ...")? **Why not make Ash Wednesday into a "holy day of obligation"?** Wouldn't that day be at least as important (spiritually) as the 3 (out of 6 non-Sunday days) dedicated to Mary? (I'm also surprised that Good Friday is not in the list either, but I don't want to clutter this question).