With respect: I do get amused when I read about those that had rock damage through their PPF, and follow it up with a version of "it did no good".
I was lucky enough to be at the Auto Salon that did my PPF and coating, and saw with my own eyes a BMW that had only half of the hood PPF'd originally. (never understood only doing half... the line is unsightly, in my opinion)
I got there after they had removed the PPF, but before it went to the paint shop, I assume. If I remember correctly, I was told the BMW driver was behind a truck on the highway that had a bunch of gravel or something just fall out of the back... something like that. Nonetheless, there was quite a bit of damage to the front of the car, as well as a nicely cracked windshield. However, you could clearly see the difference between the two halves of the hood. The unprotected upper portion had chips that were quite visible... but the front, which had PPF (Expel, I think) had what I would call 'divots'. Only noticeable due to the black paint, probably.
IMHO, those that don't have PPF, and/or have removed said PPF for any number of reasons, and say they 'haven't had any issues' without the PPF are simply lucky. I see protection as a form of insurance: glad to have it when needed... but I hope it's never needed! Peace of mind is worth it. For me, at least.
If someone had a large rock hit a protected (read: PPF'd) portion of their vehicle, and there was damage to the paint... I don't think you can truly argue the fact that the damage would have been worse (probably much) had it not been protected.