Growing up too fast

In September I turned 18, and the same day I moved out of my parents house into my boyfriends house. I still have high school left to finish, but my parents house with 4 siblings was not a possible option anymore (for me personally.)  why does everyone think it's so obscene that I live with him? We've been together for 2 years, and with me being 18 it is entirely legal. We both have our own jobs and make our own money, split bills, and both contribute to cooking/cleaning. We don't drink (however I do smoke a bit of pot for anxiety) and we just get excited to come home every night and get to talk and cuddle until 1 am. I think this is good for me, why am I getting grief for it?