>> Because health insurance is so expensive, the costs can be non-trivial and not hiring older workers can be economically rational

That is not rational- it's selfish and greedy. It's also very short-termist, because everyone grows old eventually (or at least hopes to). If we all don't hire older people, we'll all be without a job further down the line.

Failing to establish the conditions that will allow older people to be employed is not being rational. It's being completely incapable of thinking more than a few years into your own future.

Honestly- when did "rationality" become synonymous with "tunnel vision"?