Do these plastic films prevent screen damage in such cases?
If folks like screen protectors, there's lots of options for them. Me: I don't like cases on my iPhone, my less a screen film.
Screens are very durable now, made of glass. It's quite different from the days of plastic-screened Palm Pilots being rubbed by stylii. I don't see any benefit that's worth the cost and annoyance on my iPhone. So far, six years since my first iPhone, I've had no screen scratches.