I'd say its a question of accessibility and ability. I'm an Arma noob (one with grey hair, perhaps I'm a groob?!) so I'm not very good unless its being shot in the face in which case I'm an expert.
I haven't even scratched the surface of the game and to me it is stunning and incredible but the appeal really lies in multiplayer. But accessing it to achieve what I want has issues; I don't want to burden a group with my ineptitude and I just don't have the time to join a clan/squad and do lots of training. Wasteland provides a multiplayer experience, albeit a shallow one, and is easily accessible to the noob player who is trying to come to grips with the game. I imagine that over time new people will gain confidence to explore other game modes and accordingly move away from wasteland/life into more team co-ordinated play.