I have never worked at a place where I didn't need manager approval for my PTO. That includes places where I had a set PTO balance.

In my experience, having banked PTO days doesn't actually give you any real protection from abuse. A manager can still deny every single PTO request or load you up with so much work that taking any PTO will result in you falling behind. The only difference is that the company then needs to pay you out for those days, which isn't nothing, but it's also not a ton of protection from abuse.