I have never thought of cleaning tip on the floor... Never seen anyone else do it either. Sounds like a strange habit.
Very common some places. I would say it is about a 50-50 thing in some pool halls I have played in. Lesser players see better players doing it and soon it becomes the way things are done. Interestingly I have seen room owners do it.
You may get the chalk off but it seems rude. The other thing, I am more concerned with what I pick up off the floor than what I put on it. I have seen tips fly too.
Hu