Good question. I have slipped on wet floors before. One time smashing both my elbows, as My legs flew out in front of me and I landed heavily on them. Probably looked really funny, but it damn well hurt and now I suffer from arthritis in both.
If a person does not see the Wet Floor sign then they are obviously not watching where they are walking. There really is no excuse for that. Wet floors however are a real hazard, as you often can't tell that they are wet. Slipping means you can end up falling all sorts of ways and doing some very nasty damage to your body.
Hope this helps.