Why is it bad to sleep with contacts in?!

Why is it bad to sleep with contacts in?

The eye doctor says "dont sleep with your contacts in." Why is this? I know that my eyes always feel dried out afterward, but is there some more serious result I don't know about?

You should not sleep in your contacts because bacteria build up on them and if the are not cleaned this could give you an eye infection that could result in blindness. You also shouldn't sleep in your contacts because technically contacts are not the healthiest thing for your eyes because they rub against the cornea each time you blink and when you sleep you go through REM sleep when your eyes move rapidly as you dream, think of it as something constantly rubbing against your skin, not hard, very gently. It doesn't cause much damage and your eyes recover very quickly but it's still best to give them a rest at night and let your body do it's thing. I know they have the monthly contacts now that you leave in for a month, and supposedly they let more air in but the best thing is to take your contacts out every night, or better yet, wear them every other day.
I know the other people say that have been doing this for years and never ad a problem, hey not everyone who smokes will get cancer and some people a horrible diet and never get hear disease, if you want to wear your contacts to sleep that's your risk, but know the risks before you do it.