The problem with those value-adds is that they're priced completely out of the range of the utility you might get out of it.
Remember - little things. Yeah, having a few more inches of legroom would be nice, but $50 nice? I'm well over 6" here, and the seats are designed for the lowest common denominator. Unless I get a reclining seat in first, it's gonna suck.
Priority boarding, I never understood the point of. Okay, you get on the plane a bit faster to spend more time in tiny seats. If you didn't get a window seat, you're still moving over people. For another extra $30 or so.
Say I get 'em both. I've spent an extra $80 on a ticket, and from there, I'm about halfway to first class. The extra ~$120 would get me more legroom and a mediocre meal that I could have gotten in the airport for a tenth of the price and some positive multiple of the quality. Some might bring up the free drinks at this point, but I swear the FA's are trained to tactically ignore you after about two drinks.
On top of all that, there's the psychological aspect. It feels scummy and exploitative (indeed, it is scummy and exploitative).
So a victory for the "market", I guess, at the expense of basic humanity.