Also, most doorknobs are screwed on. It's going too far to drill and screw holes into someones door.
I don't know if it's universal, but at least sometimes, they're not just screwed into the door. a rather big hole is cut into it, where the inner parts of the knob sit. then the two outside parts are connected to each other by screws
so you'd have to not only cut another hole in the door (which would be difficult to repair, and probably affect, to some extent, the structural integrity of the door), but also leave a big, obvious hole in the other side
flipping a doorknob around could be a nice prank, because it would be a relatively easy fix
but given the fact that, like I said before, they will generally open whichever way you turn them, it wouldn't make a big difference (and also it wouldn't work with doorknobs that are handles as opposed to... knobs)