Ageism is just as inappropriate as sexism or racism. The tech industry seems to be going through growing pains with respect to sexism, but ageism is apparently still widely acceptable.
At some point in life it becomes hard to do something you have not done before. You can get better at what you are already doing (e.g. Going from 20bn to 40bn like Warren Buffett after 60), but it's harder to go from 0 to 1m, since this involves new stuff, a qualitative change.