I think it depends on whether person remains capable of performing the job and/or whether anyone else's safety is put at risk by having, say, a seventy-year-old do that job. I know of a professional guy who works in an office-type setting (as opposed to being someone who pulls people out of burning buildings). That guy was hired into a fairly high level position and has for ten or so years. He's just an example. Someone else I know was forced into retirement because her company had to trim out people, and close-to-retirement-age people were among the first to go. She just went out and got another similar job. People over fifty-five can still have kids in college they'd like to help. They still have mortgages and rents and heating bills. Having little kids can be a whole lot less expensive than having just grown, and in college, ones.
Also, another question might be this: Since science now knows that the human brain is not completely developed until "early- to mid- twenties", should everyone under twenty-five be forced to remain unemployed because "often people under a certain age can't do a job as well, or doesn't have the same maturity in judgment, as someone older does? "But someone sixty-two may die or leave in two years." So may someone twenty-six. Then again, someone in his sixties may stay for ten years (like the guy I just mentioned) because he keeps getting more responsibilities, likes his job, and is far too active and vital to go sitting in a rocking chair somewhere.
Who gets and keeps a job should be about who can prove, has proven, continues to prove, that he's able to do the job well (again, with the exception of the kind of job that could mean that the person's having a heart attack (or something like that) could immediately put the safety of someone else at risk). Even with that, though, younger and irresponsible train conductors and bus drivers have been known to kill themselves or someone else by texting when they work; and similar is true for people of all ages who drink, use drugs, take ridiculous risks, or do any number of stupid things on the job.