I've woken up dozens of times with new cuts. I have no idea how they came about, i have no recollection of them. Just this week i woke up with three cuts on my thigh, i have no clue how they got there.
I don't think it's something specifically done intentionally. I just fall asleep with it so end result is cuts on you when you wake up. Otherwise the point is usually to feel the process/action, as adam said.