The U.S. government imposes numerous rules to keep commercial airline pilots scarce. This is done under the guise of safety, but the rules don’t actually have anything to do with safety.
The problem is that more available pilots means less leverage for pilots unions, and since union contracts determine who flies which aircraft, which routes, and which schedules – and therefore how much a pilot gets paid – largely based on seniority, a higher retirement age while good for older union members is bad for younger ones.