I’d say inertia and unawareness of the FAANG salary market on the supply-side, and ageism and preference for demographic diversity over experiential diversity on the demand-side.

TBH A range of ages is demographic diversity. No idea why it's forgotten about sometimes.

I suspect there isn't an even subconscious effort to exclude people of age, but that it's a side effect of the FAANG interview process. People who have been in the industry for decades don't care to learn to do leetcode interviews when they can get paid perfectly well somewhere either based on connections, or by going through interviews more centered around job experience. That said, I doubt a person making 60k somewhere would have made it in to a FAANG at any point. Making that little in the modern tech market shows either a lack of skill, a lack of desire to improve one's salary, or a need to live and work in a location where there aren't many opportunities for employment. There are plenty of non-faang places that are desperately hiring for 6 figure salaries at this point.

>That said, I doubt a person making 60k somewhere would have made it in to a FAANG at any point.

Well you're dead wrong about that.

For some reason I think places like Microsoft have plenty of old white highly experienced embedded engineers that could work on a web app if they wanted to, I just don't think they could do any better.