It's always good to have a game world that encourages party play - i.e., it encourages player characters (PCs) to hang out in a group and get involved in plots as a group. In some games this is institutionalized; there are specific mechanisms for PC interaction ("Werewolf's" packs (White Wolf); "HackMaster's" adventuring companies (Kenzer & Co.); "Doctor Who's" group of Time Lord-plus-companions (FASA)). Such an approach can be extremely helpful to PCs who need an extra nudge to work together. Luckily you can take your own approach to this. If such a hard-and-fast institutionalized style doesn't suit your game, you can take a more subtle avenue.