That's just the way the game developers decided to do it- Namco Bandai went for an actual world wide access while Insomniac decided to keep the online side of their game regionalized (probably in part to make sure players can understand each other in chat during play). There is no voice chat in RR7 so something like that wasn't really a concern.
Most of the games with online play are probably going to use regional servers- if you want to meet up with people to play online you'd best get the games from where the online play is more popular (online console play isn't that big in Japan or China, it seems).