Does anyone know why profanities are beeped out on the DVD's?

Obviously they are going to be beeped out when they're on TV. Then I got the entire series on DVD and was looking forward to hear everything not beeped out, especially the really long parts that are beeped. Is there are reason as to why they are beeped out on the DVD's, and also if there is a way to find out what was being said?