Competition and personal achievement. At least for me it is. I'm rank 1 and looking to break into Legend before season end. There's no extra reward that I know of. But its the ambition driving me.
if I can make Legend this season, then next season I should be able to climb up from 5 again in fairly short order, then spend most of the season climbing the numbers in Legend.
I like the psychology of the game, recognizing players I've played before, identifying play styles, outfoxing an opponent and just making rank.
And who knows what awards await us further on down the line. The game is still fairly in its infant stage, dev's are improving and changing up frequently. So who knows what's in store.
But for me. It's competition, and achievement. I want my spot on that top 100 list.
And that's just for starters.