So how many days do you take a year? As the other comments also touch upon, it becomes an outperform thing with co- workers, to take the least amount to "perform better". Also how easy and often do managers then deny requests?

With a fixed set it has an actual value, at the company they can't deny PTO's as they are yours. Of course planning comes into play a little bit, but if you let the company know that 2 months from now you take 4 weeks off for a good long summer holiday, that is what you will be doing then in those 2 months.

ps. I have 25 personal paid days, a bunch of public holidays. Doctor's appointments are on the 'please try to schedule them outside working hours if possible, otherwise, well, that's life, you need to visit that doctor'. Full travel reimbursement (fixed amount per month, can spend however i want), A lot of secondary items in my contract as well dealing with having to take care of partner / children if they become sick (is paid time off), etc etc.