Why does diamond rank even exist?

I've gotten diamond each ranked series and feel the same. So far I've quit playing ranked as soon as I get to diamond each time, it's just not fun.

At least if it was plat straight to pred, maybe I'd have incentive to play because I'd be part of the pred club against other preditors. Plus, I'd probably fight for my world rank more. 

As it stands, getting to diamond for me just means not playing ranked the rest of the season.