[mbrukman]

Note that I'm not the owner/developer of that site, so I can only guess how it's implemented there. However, I can give you a general overview for why logins are typically required for such use cases.

While you're correct that cookies is a good way to identify users, they could be faked by other users (to steal or change your saved games), which is why websites typically have user accounts where you have to prove you know something (such as a password) in order to claim to be user id 12345.

If you don't have to prove anything to claim to be user 12345, then some creative users on the internet will write bots that will claim to be every possible user (in sequence), and either trash or delete their saved games, or do something else to affect them in the future.

Thus, we have the need for user accounts on websites to securely identify users and their settings, saved games, shopping carts, purchase history, etc.

If you're interested in learning more, take a look at:

* https://en.wikipedia.org/wiki/HTTP_cookie

* https://simple.wikipedia.org/wiki/HTTP_cookie

Hope this helps!