.... Also in large cities there are offices that exchange cryptocurrency for cash, there have been no problems with this for a long time.
Perhaps in your country, because in mine those offices or places for people to exchange cryptocurrency for cash are non-existent, mostly because the fer people have to the government of this country to seizing their assets and holding them without a legal reason.
Instead of offices which exchange crypto for cash, we still have physical casinos, which allow people to gamble their chips without a clear and well defined limit.
So, from my appreciation, it is more likely for someone in this country to use physical/brick and mortar casinos to conceal the origin of their money rather than going straight to cryptocurrency casinos, which will almost certainly ask them for identity documents.
Those offices you talk about must at least ask for a minimum of documentation, otherwise they would end up with coins gotten from hacking and theft.
Regarding crypto, I think almost every country will have its own regulations in its use, even some countries may have been able to accept it as an investment asset but there are also those who cannot accept it for various reasons.
If in context like this, I would think much more that hiding assets for specific purpose and utilizing gambling sites has indeed occurred a lot and it will be kind of money laundering and basically they do this to be able to eliminate the history of the origin of the funds obtained.
Previously, identity verification such as KYC had not been widely established by several gambling sites and the chances of something like this happening were much easier, but now I sure something like that is much more difficult because of several KYC regulations.
From what @nimogsm said maybe it could actually happen there but we wouldn't know what is actually done in how such an exchange works, there might also be requests for various documents as you have mentioned.