user4399: For simplicity, let's focus on just 1 time control.
In chess.com: I've previously reached a peak rating of 1360 under a starting rating of 1200. Then I stopped playing chess on chess.com for awhile (e.g., I went to lichess or chesscube or chess24 only). During this time, chess.com changed their rating policy to allow people to choose their starting rating between I think 400, 800, 1000, 1200, and 1500.
Question: What's the benefit / point of this really over just keeping the starting rating at 1200? I see this as pointless and confusing particularly for players who started in the old policy?

user12629: 
But that applies to your 1st few games only? After 10 games, it doesn't matter anyway?

Yes, but the first 10 games matter in themselves for one reason: the first impression of the site. If a new casual player loses many games in a row to start out, they may think the site is too difficult and leave, and obviously the site wants to avoid that. Starting too high will also make their "max rating" statistic be higher than anything they could actually obtain.

And in the long run, if there are still people like you, then why wouldn't they be harmed from choosing 1500 given that '1500' will actually be 400 points stronger than the previous '1500'?

Lowering the initial rating will, over sufficient time, cause the established players' ratings to be lower than if you hadn't lowered the initial rating. That does not, however, necessarily mean that the established players' ratings will be any lower than they used to be. There are various inflationary and deflationary factors; initial rating is just one of them.

I mean in 2023, who has a FIDE rating but not an account in both chesscom and lichess?

This got me to thinking. When you create a chess site you initially get players of all strengths. But if all the strong players already have accounts because you've been a popular site for many years, wouldn't that imply that the average player making a new account now is weaker than the average player making a new account when you started the site? Especially if, say, a pandemic caused people to have a bunch of free time and a miniseries increased the popularity of chess among people who hadn't played much before? It's entirely possible that, because you're attracting a different class of player, the initial rating might have to be adjusted to keep the current players at the same level. (I do not know if this is indeed the case; only that it is possible.)
But one advantage of letting the players select is that variations in strength are somewhat accounted for. If the NYC public schools suddenly put chess in the curriculum and forced every one of their 920,000 students to make an account, the kids could set their rating to 400 or 800 and that would reduce the impact compared to if they all started at 1200.

user4418: 
What's the benefit / point of this really over just keeping the starting rating at 1200?

The benefits are obvious. If you pick your start rating honestly then you will get better games. For instance, my FIDE rating is just over 1700. If I choose 1500 as my start rating on Chess.com then it will match me with players who will give me a much better game than if I started at 1200. Similarly a beginner would get much better games starting with a much lower rating than 1200.

4399: <p>For simplicity, let's focus on just 1 time control.</p>
<p>In chess.com: I've previously reached a peak rating of 1360 under a starting rating of 1200. Then I stopped playing chess on chess.com for awhile (e.g., I went to lichess or chesscube or chess24 only). During this time, <a href="https://chess.stackexchange.com/questions/8925/starting-elo-rating-at-chess-com">chess.com changed their rating policy to allow people to choose their starting rating between I think</a> 400, 800, 1000, 1200, and 1500.</p>
<p><strong>Question: What's the benefit / point of this really over just keeping the starting rating at 1200? I see this as pointless and <a href="https://chess.stackexchange.com/questions/41462/chesscoms-new-policy-allows-users-to-choose-starting-rating-is-this-actually">confusing particularly for players who started in the old policy</a>?</strong></p>
 12629: <blockquote>
<p>But that applies to your 1st few games only? After 10 games, it doesn't matter anyway?</p>
</blockquote>
<p>Yes, but the first 10 games matter in themselves for one reason: the first impression of the site. If a new casual player loses many games in a row to start out, they may think the site is too difficult and leave, and obviously the site wants to avoid that. Starting too high will also make their &quot;max rating&quot; statistic be higher than anything they could actually obtain.</p>
<blockquote>
<p>And in the long run, if there are still people like you, then why wouldn't they be harmed from choosing 1500 given that '1500' will actually be 400 points stronger than the previous '1500'?</p>
</blockquote>
<p>Lowering the initial rating will, over sufficient time, cause the established players' ratings to be lower than if you hadn't lowered the initial rating. That does not, however, <em>necessarily</em> mean that the established players' ratings will be any lower than they used to be. There are various inflationary and deflationary factors; initial rating is just one of them.</p>
<blockquote>
<p>I mean in 2023, who has a FIDE rating but not an account in both chesscom and lichess?</p>
</blockquote>
<p>This got me to thinking. When you create a chess site you initially get players of all strengths. But if all the strong players already have accounts because you've been a popular site for many years, wouldn't that imply that the average player making a new account now is weaker than the average player making a new account when you started the site? Especially if, say, a pandemic caused people to have a bunch of free time and a miniseries increased the popularity of chess among people who hadn't played much before? It's entirely possible that, because you're attracting a different class of player, the initial rating might have to be adjusted to keep the current players at the same level. (I do not know if this is indeed the case; only that it is possible.)</p>
<p>But one advantage of letting the players select is that variations in strength are somewhat accounted for. If the NYC public schools suddenly put chess in the curriculum and forced every one of their 920,000 students to make an account, the kids could set their rating to 400 or 800 and that would reduce the impact compared to if they all started at 1200.</p>
 4418: <blockquote>
<p>What's the benefit / point of this really over just keeping the starting rating at 1200?</p>
</blockquote>
<p>The benefits are obvious. If you pick your start rating honestly then you will get better games. For instance, my FIDE rating is just over 1700. If I choose 1500 as my start rating on Chess.com then it will match me with players who will give me a much better game than if I started at 1200. Similarly a beginner would get much better games starting with a much lower rating than 1200.</p>
