I don't really see how last-hitting is all that different from kills in, say, FPS games--if you land the killing blow, you get credit for the kill. There's no kill assist going on, though. I guess the fact that a huge part of the game is getting said last-hits on creeps is different, as opposed to killing players.
Of course, I've only played DOTA 2 at a low level, so I don't know how the mechanic translates in other similar games.