(Snootysims)
The ESRB, the company that decides the age rating for games, gave a teen rating for Sims 3. Not very surprising or interesting but the official, serious reason is actually quite hilarious:
Sims characters need to maintain their health and hygiene and do so by eating, exercising, bathing, and using the toilet, which is depicted by a blurred, pixilated effect and trickling sounds. Avatars can also vomit, emit flatulence, and wet themselves if no toilet is available.Check the full text here:
http://www.esrb.org/ratings/synopsis.jsp?Certificate=26182