We call them "nail pops".
First, are you sure they are screws? Nails are common here. When the wood dries out, it shrinks and "squeezes" the tapered nail and it will back-out slightly causing the "nail pop". The only fix is to drive them in and re-tape, texture, and paint.
Second, we don't glue wallboard to the studs. So, often the wallboard stands "proud" of the wall (stands slightly away from the wall). This can be caused by the studs not being set in a straight line, the stud is slightly warped, etc. So, after the job is complete, someone will bump the wall causing the wallboard to bow (flex) in, but the nail does not move, thus the "nail pop". Again, the only fix is drive them in, tape, texture and paint.
When we use screws, we don't have these problems. The screws seem to suck the wallboard up tight to the framing and not "back-out".