Because it focuses on being family friendly with its games and marketing. If they didn't want that stigma then they would be doing the opposite. Their web site looks like a kid store. In each rating, Nintendo has twice as many E, E10 and teen rated games each compared to M rated games. Sony has twice as many m rated and teen rated games each in comparison to E and E10 games. You see the difference in focus? The only ones who really care about that stigma is the older ninty fans. It doesn't affect any other gamer fanbase.