Basically its for player retention. Folks got butthurt and quit playing the game when they only ever saw their MMR sink.
Ranked participation increased when Riot gave people shiny fancy Icons and ranks. Riot has some "casual" aspects added to their ranked ladder for folks who cant make it out of the majority MMR. Demotion protection range is massive and Duo range is also massive. Not ideal for strict quality but then again the average MMR is used to build the skill curve by Player's result comparisons so its got the most mismatched games.
Its not that hard to ball park MMR. Look for the consistent match average in recent games.
Your at S4 MMR for the most part, low # of games thou. Keep winning and your gonna skip entire bronze divisions.
https://na.op.gg/summoner/userName=notnotkaiguy
I went out of my way to separate this accounts Rank and MMR by using things that Drop LP but not MMR. Skipped every promo from B1 to S1. Eventually had to play a series for Gold as it was getting to time consuming to keep failing Promos by dodging lobbies.
And seeing the points is basically worthless for players as well. It's build around an Arbitrary variable system so Riot would have to provide their starting MMR value, Their Distribution Model, and how many points makes up their class intervals.
Example. the number 10, It can be 10% or 100% depending on the scale being used. 10/100 points, not all that good but 10/10 points the best you can get.
Some folks will say some incredibly stupid shit like "Its so they can rig games to make it more grindy!"
when by design systems like this have a time to climb for the average player of Eternity. Yea...brilliant argument Rito wants to make it go from infinity to infinity +1. What solid fucking logic that makes.[zombie-brand-facepalm]
So then some folks will change the argument from Eternity +1 to Big bad riot wants to make your climb to the correct rank Take longer and hidden MMR allows them to Rig games to do so. Which is batshit insane as Riot controls the Max and min # of points you can gain per match so if they wanted to add time to grind to your "true" Rank. Rather then Try and control human behavior and hope the right mix of RNG players is online at any given hour of the day and hope they all behave the way you need... they could half the point gains. Which on a minimum will double the time to reach the right rank with a single value tweak impacting 100% of players.
Some people... have 0 accountability and will never ever stop looking for an excuse.
anyhow
TLDR.
its to distract people who get stuck and the folks who sink.
