Swearing isn't immature lol. I swear at school a lot...I mean ALOT. But it doesn't make me any dumber. And it's considered an "adult" language because you wouldn't really want young children going around cussing each other
Some people don't think it is immature. Some people view it as a good stress reliever. The trick is to use it appropriately. Swearing in preschool is not ok. It's not advisable to try it out in church or when yelling at your parents either.