Either way, if you take a RB #1, you're probably dumb.
If you have the #1 pick, your team sucks. RBs can't produce for themselves (perhaps Barry Sanders excepted). They need an offensive line. If you're so bad that you've got the #1 pick, you probably have a sh!tty o-line. A running back isn't going to help you.
The same is somewhat true of a QB. If you have the #1 pick, you probably don't have the o-line or the offensive skill players to support that QB. That QB--who will be expected to pretty much start immediately--is going to be shell-shocked by midseason. Probably [especially] because he's used to playing on an Alabama or OSU or [insert helmet team here] squad where he's been surrounded by players who have a talent advantage over every single team they face short of the CFP.
Teams keep doing it. Teams keep failing. I'm guessing it's not stupidity. I'm guessing it's pandering to fans who are going to roast a GM if they take a can't-miss LT or edge rusher #1 because their fans look at their sh!tty QB (who is mostly sh!tty because he's got no supporting cast) and want to replace him first with the hottest name on the market even though they don't have the supporting cast for the next guy either.