This would be your choice to make, and it seems you get to make it. Great! But the point is: so many do not because employers make it for them by discriminating against them based on their age.
I'm fairly sure those criteria are all illegal, at least in most U.S. states if not at the federal level.
Also, it's a huge leap to say that discrimination is motivated by profits. I have no idea how you worked that one out.