Also because that person is the most visible.
Brown nose to get into a job, and then wreak invisible havoc, undermining the brown nosers with nasty rumours
Sadly, it doesn't. Often your ability to "redistribute" work to your colleagues makes you look more impressive, while at the same time diminishing their work throughput
Every day that you don't have to wash your nose is a Good day
In Oz, we have a decent FREE public health system, which our government is hastily trying to sell off to corporations, so this is not an issue here.
On the other hand, a 20yr old is less likely to have existing medical conditions than an older worker, hence the corporations insurance premiums are lower. So they will continue to avoid older workers until there is a drastic change in attitude & they pursue positive attributes (like experience & knowledge), rather than the singular pursuit of money, which looks good on paper.