I have never ever used a screen protector and I have never had scratches on my phone screens. 5+ different smartphones over the years. Can say the same for my partners phones, since she usually gets my old device when I get a new one.
Not saying that to discredit your experience, maybe you work around a lot of dust or some other conditions cause that. In my case I just simply never had the problem to begin with.
Yeah, maybe anecdotal for me, definitely aware of that. But I swears! And multiple devices, multiple different pants pockets. I never put anything in the same pocket with the phone though. Not sure what’s the defining factor here.