Почему на чес коме так много людей с рейтингом ниже 600?

почему?

Because there are other people on chess.com who do not let people under 600 get above 600

So, is the rating useless for such players? Then what's the point of adding it?

Ratings measure the relative strength of players within a certain chess community

Yes, but it could happen that a player with a 1750 rating plays against a player with a 1000 rating, and who would win then? Of course, the player with the 1750 rating would win, but both would have a 900 rating.

I did not understand this part

am writing in Russian, please translate it using a translator.
если встретяться два игрока у которых рейтинг 900, а сила игры абсолютно разная, то тогда в чём смысл рейтинга для таких игроков?

If your strength is 1750 but your rating is 900 then you should play some games until your rating gets closer to your strength and stabilizes there. This process usually takes short time

Yes, but you said that Chess.com sometimes doesn't allow rating increases, and players are left with a rating that doesn't match their play.

If you have played like 10 games and you are still 900 then your strength is 900 and not 1750

Chess.com has a tool to evaluate a player's strength in the game report, and the player's strength is 1750, but his rating on Chess.com is 900, and my rating is not 900, in case you thought I was talking about myself.

I did not mean exactly you by "you", that was just an example.

As for the magic number from game reviews... All I can advise is to not take it seriously

OK, thank you!