Since everybody is talking about MMR
Why does it exist? I get that the point is to match you with players of the same skill level as you, but isn't that what ranks are for? The fundamental use for a ranking system is that if you win, you get rewarded by moving to a higher rank. Wouldn't it make more sense to place people up against someone their own rank and if they get on a win streak, reward them with more LP? Instead of placing them against someone of higher rank, move them up to that rank.
But I'm actually asking, because I don't know much about this topic, are there any inherent benefits to the MMR system over a much more simple ranking system?