I'll tell you right now. There is ABSOLUTELY discrimination against older workers. Even though most workers these days don't stay at companies for more than 5-10 years, if a worker is "too old" they think they'll be too hard to train, or "just looking to retire"--even if the length of time is the same.
My father is the pinnacle of excellence and professionalism as a plant engineer. Everything that got me ahead of my fellow students and into a Ph.D. program, I owe to his teaching and critical thinking. He walks into a building and immediately notices things that can be improved and will save them money. (And he's not a jerk about it, either.) He worked for a company for 25 years, and others almost as long. And ever since that 2008 recession? He's been out of a job. His plant got bought out and sold off. They kept him on longer than anyone else because he was one of the best employees they had--but the company eventually went away.
And now? Nobody will hire him even with countless references from management to coworkers. "He's too old." And one recruiter literally told him that.
Imagine how depressing that must be, to work your ass off your whole life and doing "the right thing", putting in 110%, going into work at 3 AM because "the line is down!" and what's he got to show for all that extra work? A dwindling savings account that was supposed to be for retirement, and countless rejections from companies who wouldn't know a good employee if it smacked them in the dick.
That's not how you treat the people who literally built the infrastructure you grew up on. It's reprehensible. And I cannot, for the life of me, understand why anyone (with a brain) would really care about age when all that matters is: "Can you make me money?"
Someone may say, "Well, they can pay a junior engineer less money." Yeah, and a junior engineer is going to have less experience reducing costs, and improving reliability. There's a reason we pay experienced engineers more. Because they add more value for a unit time. It's not like we just go "Oh, you're older now. So here's some more money."