I would just think of it as buying all the parts in one fell swoop.(Just stirring it up in The Pasture. No AR's or AR builders were harmed in the making of this post, and no offense intended )
If I was depending on an AR for my family's life or other self defense, why would I buy someone's homebuilt version rather than spend a few hundred dollars more for one from a respected manufacturer with well defined QC processes and thousands of rounds tested?
If it is just fun for plinking, don't I still have to make sure the barrel nut was torqued to spec, headspace etc etc etc? So why wouldn't I just put one together myself and get all the parts I want in it and know for sure it was done right?
Headspace? Why does everyone like to talk about headspace? Unless you're installing your own barrel extensions, which no one I've encountered does, that really will never be an issue. The first half dozen or so that I built I had heard all this headpsace nonsense, so I developed my own method of checking headspace. On the first shot I squint my eyes and turn my head. After that it's not even something I would waste my time thinking about.