The assumption that we're slower, out dated and unwilling to put the hours in is kinda prejudicial. Some of us may be, but TBH I see a lot of foolishness, wasted time and nonsense from some younger people too. Enthusiasm and Wisdom are BOTH valuable. A trait that might be more common in one age group is not justification for rejecting the entire age group.
But the hiring processes are totally discriminatory. I've been on the other side of it too often, seen bosses reject people younger than me as "too old" without even realizing it (or that they are creating cause for a discrimination lawsuit.)
Last time I interviewed with bay area startups I had a %100 correllation-- visual interviews (eg: skype video etc) would not progress, even past the HR initial contact (eg: no technical interview at all) while ones done via audio (no visual) would progress. (I guess I don't look as young as I think I do!) We're talking well known companies like Digital Ocean and Stripe engaged in straight up age discrimination.
After being discriminated against by Pebble a few years ago, I figured they were the exception (The guy who interviewed me was so young and so incompetent the he had the wrong answers for his trick questions and couldn't grasp my explanations, which the HR lady reported to me as "you need to get stronger on these things")... but the most recent round convinced me that it really is discrimination.
I've got a lot of really valuable talents and relevant as I've stayed current. I interview very well- typically I can get a better job than I deserve by interviewing. I've been rejected lots over my career, sometimes just arbitrarily. I never would have thought that I was being discriminated against except that I noticed the correlation between visual interviews (and I'm certain that 5 years ago when I was rejected I was not being discriminated against.)
Further, as a sexual minority, I had to deal with the possibility years ago that I would be fired if people found out. I decided that this was fine-- I don't want to work for a place that discriminates against me. I can make money on my own if I need to, I don't need a job.
So it's no big deal. I'm just surprised at how poorly so many companies do it. And of course, I do tend to stop being a customer of companies that engage in discrimination. (That's me discriminating against them. :-)