Let's say, for argument's sake you're in the middle of the pack-- so if we're using bronze, silver, gold, and platinum (for the highest 2% or something), you're firmly in silver. You like to win and progress as anyone would, but there are a lot of games out there and/or maybe you don't have all that much time to dedicate to one game.

In this scenario, which is where (I imagine) a lot of players fall, including "invisible MMR" and ranking echelons makes a lot of sense. If I'm playing and constantly seeing my score go down-- Hell, even maybe for the first game of the evening-- one may get either demotivated or angry and quit. In that scenario, either I'm done for the night or I switch to another game (likely one at which I'll see some measure of success). With so many competing games out there, any system is built to maintain or build player base, right? In my opinion, the echelon system allows for decent matchmaking while allowing the illusion that one isn't suffering too awfully much for a loss (and, ergo, may increase one's likelihood to continue to game).

This doesn't detract from anyone who's a hardcore gamer, however, as they have a plethora of stats they can track (either on a site like halotracker or manually) as well as watching replays to see their strengths and weaknesses in order to improve on them. MMR factors in many things-- not all of which may necessarily matter to someone who's competitive-- and showing it can adversely affect the morale of someone who plays. Hell, say I win but I had kind of a shit game and pulled somethin' out of my ass last-minute (or my team carried me)-- my MMR won't help me analyze a damned thing in that scenario, right?