There is a lot of debate about the ratings systems in place today. People seem to think it's suppressing art.
Personally, while I don't think they are perfect, I like having them. I almost always rely on some form of content advisory when going to see a movie (mostly IMDB and Plugged In), but having a big PG-13 on the sign helps the decision making along! You know what to expect going in.
TV also has a rating system. So does music... however, I've never had to use that one!
What confuses me is why books don't have ratings. Yes, there are a lot of books on the market. Around 300,000 were released and re-released last year alone... however, it's weird there isn't some sort of system in place.
There aren't even content advisories. Plugged In will review hip new books and Common Sense Media has a few... but it's hard to find a consistent source for content in novels.
I've started reading a couple of books only to bail within a couple of chapters because of excessive harsh profanity or lewd content. These aren't even obscure or edgy books. One is considered to be the grandfather of science fiction. The other was 1984 which is taught in high school... which I guess means I'm being too uptight? I donno... I thought it was a little racy.
Book industry - Get your junk together and start putting content advisories on your stuff!