Actually, older workers understand proper working conditions, tend to know what they are entitled too and also tend to have higher expectations given the quality of the working conditions.
Young workers are easy to bully, will do more things outside the scope of their employ (far easier to exploit into working far more than they should) and can be bought for much cheaper as they have less expectations going in.
Ageism is hard to prove because it’s more about the correlates that come with age and experience over the fact your this number of years vs that guy who is that number of years.