I’ve always heard there are two big reasons for age discrimination:
1. Older people will cost the company more in health insurance on the company health plan.
2. Older people expect to be paid more than younger workers, so employers tend to go for a younger hire.
Age and experience will be advantageous, if one is being recruited for an executive or management level job. But for the bulk of jobs out there , employers prefer to hire younger people.
re number 1
Maybe just me and my experience but I am on work earlier, stay longer, and miss more days than everyone 20-40 years younger than I am. Basically I take a PTO day for my annual physical and that is the only health related time I am out each year (doesn’t mean I never get sick, just work through it). So 1 doctors visit per year and a recurring prescription I take that is cheaper to me if I don’t file it on insurance per year.
Young workers tend to be more grateful for a position, and have less demands.
Don't forget the third big reason, which is rarely admitted. Younger, less-experienced managers often feel insecure around older, more experienced staff. And they may have authority issues with parental figures which make older workers very unappealing to them.
There is no solution to this problem but to move on. Chronic labor shortages tend to improve the situation.