Why do volleyball players wear knee pads?

I think that they do this to protect their knees from impact with the volleyball court. This could cause an injury to the knees, or at least bruise them up. In the volleyball game there is very much diving for the ball, kneeling to save the ball("knee save") and even if you know how to dive correctly, you are at great risk of hurting your knees. Additionally, women/girls don't want to have any bruise/ scrape on their knees, because they want to look beautifull and probably nobody thinks that these scrapes, bruises or floor burns are something pretty, interesting or sexy! I noticed, that the difference between women and men in wearing knee pads in volleyball is very great( of course more ladies wear knee pads than men).