It's down to the parents. The teen rating is merely a guideline. My 9 and 10 year olds play destiny with me, the ten year old has done all the raids on hard. In my family we get together and save the universe. A lot of my friends have kids who play, so it's often a big family outing to the dreadnought or into crucible. The kids are being taught online etiquette rather than being dumped online by uninterested parents just wanting an electronic babysitter while they watch big brother 342.