Love how people who don't care about ranks dismiss it as "e-peen" as opposed to a measurement of skill between players. I don't mean to be abrasive so don't take it like that please. But ranks are more than just bragging to a bunch of people that you're a general blah blah. It let's you know how good you are relative to the other players in a game. The ranks in Reach and Halo 4 told me jackshit aside from these guys either played the game a lot and still suck, or these guys didn't play a lot and yet are good.
I wouldn't even say I'm good anymore. But I liked knowing how good I was. What my "skill" level was at, whether it was improving, what others were at. Ranks are more than just about being "fun" but giving folks something to do, to look forward to, to continually get ranks.
The games without ranks in a sense, also had the lowest player bases and the lowest time spent playing the games. People are competitive, they want to know how they did.
And in my anecdotal experience, I've always found the guys who say ranks are useless, they aren't needed, were always the ones upset that they could barely get over 30 in a lot of playlists. I'm not saying you, but even Frankie has mentioned "e-peen" in the past, but just look at a lot of the most played games on Twitch, ranks matter.