Interesting topic ... I used to think there were more 'less mature' players training combat, simply because it made them feel powerful over others, and they liked doing damage to pixels. Without the wilderness this might not be true anymore.
The worlds make a little difference, but I'll look at it in terms of magic trees. There are magic trees south of Seer's Village, that everyone can easily access with 75 woodcutting ... so people get bored easily and decide to be immature. The trees in elven land are a little ways from the bank, require some difficult quests to get to, and it's harder to navigate to and from them, so there's not many people, yet if there are they're mostly mature.
It's a tradeoff though .. I can either go to Seer's and try to find someone to talk to yet get annoying people .. or go to elven land and find someone mature to talk to or be bored out of my mind. Oh and of course, most banks in populated cities are full of immaturity due to the player age base and the need for everyone to go there .. sadly
