Using a rating of 1200 as a starting point is a way to provide new users with a neutral or average rating. It's neither too high nor too low, and it gives users room to improve or decline based on their actual performance.
The curious case of 1200: The Expert's rating

i have been in 1200 range and in rapid some suck because they blunder but many are good. in blitz it is ok in 1200. many people who are 1200 in blitz are 1300 to 1700 in rapid. bullet is fairly good

most people below 1800 are complete trash, if you have been below 1800 and above 1800 you would know what im talking about.
When I’m playing well, I’m over 1800. When my play is trash, I’m under. Is is really that simple?
When I play open seeks, my rating rises above 1800. When I play g10 Arena, it falls below.
Maybe he really meant 1800, not 1200. 1800 is probably good enough to be an expert.

I enjoyed this article when I had just reached 1200 and it felt like a great rating to have reached and stroked my ego. Now at my peak I was 1400 and I'm back down to 1350. So 1400 is my new target and feels like a great rating to reach. Just compete against yourself and try and keep improving and whatever new rating high you achieve feels great and you deserve to feel great about it!

the first hump is 1000, the second is 1500, the third is 2200, the fourth hump is humpa lumpa dumpity pum, Stockfish still thinks you are dumb, cuz he is 4050 says humpa lumpa but it's hoompa loompa from wonka.

i think while referring 1200 as expert, the post author had in mind expert for a common people, not chess enthusiasts. with 1200 you are most likely beating all your friends with ease, and only othr enthusiasts can see the flaws in your game (unless you gave material for free that happens quite often in 1200 ranks.
I stay around 1200 in rapid and I suck. And the chess community doesn't even recognize players under 1600, they just call anyone under that class C. So I think you over estimate 1200
Fair they aren't that good tho youl always feel like you suck

The 1200 hump, as it is commonly referred to in Chess, is the sport's greatest obstacle.
Achieving this rating is the equivalent of graduating from an Ivy league School. No, it does not yet mean that you have mastered this pastime of intuition and pattern recognition. It does on the other hand suggest that you are well on your way to achieve such accomplishments.
In other words by attaining the rating of 1200, you can claim the title of being a Chess expert, and deservedly so. The mark of 1200 separates the casuals from the serious. It is the dividing line between the average and the exemplary.
I write this today because I want to address Chess.com's peculiar approach to rating new users. Many of you know that upon opening a Chess.com account, one is immediately gifted the rating of 1200. This means that every new user is recognized as an expert. Of course most of these users end up going below the 1200 mark and lose the title almost immediately, after all they are beginners and not used to such high level Chess. Does anybody know why Chess.com has chosen 1200 as a starting point? After all it's not just an arbitrary number.
I started at 400 ELO.

Back when I joined chess_com - during the late bronze age - you could ONLY start at 1200.
There were no other options.
In OTB play using classical (slow) time controls, a 1200 rating is the bottom of Class D, which is more than a standard deviation below the average club or tournament player.
people shouldn’t get upset by players starting at different ratings. The rating system is self-correcting.
suppose two players have the same „true” skill level of 1200. Now suppose they start at different ratings, say 400 and 1200.
After they play 100 or so games, they should both be rated 1200. the only difference is that one started at that level and the other took some time to get there.

I started at 400 just for fun.
This rating system shouldn't let people just pick any ol starting rating, that's stupid. But mine did average out quickly. The problem with starting at any rating is that it impacts the opponents rating more early because it's assumed they're playing a 2000 when they're really playing a 800 for example. It tinkers with the ratings unfairly.
I don’t know how chess.com assigns initial ratings.
in the USCF, ratings for the first 24 games are provisional and reflect one’s performance rating in those games. That provisional rating is then used in determining one’s opponents change in rating. This helps stabilize the ratings. So if a new player plays at the 1700 level, that is the rating used to calculate how much one’s opponents’ ratings will change.
allowing players to identify if they are beginners, advanced, or whatever is probably a sales tool yes, the ratings are inaccurate for many, but so what? The ratings are meaningless. And if one plays enough. The ratings move to the true level.
the big problem that can result from setting one’s own initial rating is inflation/deflation. If more people underestimate their starting level than overestimate it, then there are more points taken from other players than are given to other players as the newbies move toward their actual skill level this deflates the ratings and of course the opposite would inflate them.
but in the end, who cares? Ratings online are meaningless.
This is a 6-year old thread and the opening post is insane. Why is this still running?
If it's been going on for years and makes no sense, it's probably "Tradition".