Not surprising. Years ago one of my (gray haired) mentors opened my eyes to ageism in this industry by asking me to pay attention to how many programmers in the office have gray hair. Once you start looking for it, it becomes obvious that age discrimination is rampant. Some blame the young workforce on the industry being young, but the industry is decades old at this point so I don't think that excuse holds water.
Older workers have experience. Experience is expensive. You can generate a lot of revenue with workers with less experience, even factoring in mistakes, lower productivity and output, etc. Age discrimination is rarely punished, and when it is, the penalties are minimal. Incentives matter.
It's not at all clear that there a net gain here, so the situation is at best complex.