I have used them on my phone since I got my first iPhone without a home button.
They are not all the same. The high quality ones can take a lot, while the cheaper breaks way faster.
I’m certain they have saved me a bunch of screens over the years. But it isn’t 1:1 with how many protectors I have broken versus a real screen. Maybe 10:1.
As with cases, I’d rather not use them. But with the current Apple designs that isn’t really a good idea.
I usually don’t go for the privacy ones. Mostly because it makes it impossible to use the phone at an angle. Something I do a lot while cooking or taking pictures.