Media, limit-setting, and comprehension?

I have parental controls set on all of our TVS. No rated R-no -no violence-no language, certain channels are completely blocked. etc etc etc. I limit extensively what my children watch. It makes no sense for a child to watch adult themed shows, as they hardly get the point of the show. My children really do not have time for tv anyhow with school, homework, sports practices and games. There is a reason, tv, books, and video games are rated by content or age comprehension.(the golden comp, my children would not even watch, they were bored, however given the content of the movie they do not need to watch it anyhow.)