I dunno about that though Nada, games like SC2 don't have anything to motivate people besides gameplay + rating.
One could argue that games like SC2 attract a different type of player whereas an MMO would attract those who like character progression, but that can't really be proven until tested imo.
1. HotS added levelling and stuff, fake progression to make people want to play it more.
2. SC2 ladder isn't that popular.