IRS is offering $625,000 USD to anyone that can crack the Monero algorithm [1].
[1] https://www.forbes.com/sites/kellyphillipserb/2020/09/14/irs...
They would probably not exchange into USD, there are plenty of other currencies and they would probably favor a local currency.
Though, the true answer to your actual question is what the other commenter said: it's mainly due to the Russian government turning a blind eye to it as long as they don't target Russian/ex-USSR citizens. So even if you do know a ransomware operator's full name and home address and everything else you can possibly know about them, you can't do anything about it besides hope they leave the country and try to catch them then.
Because they're typically based in Russia, and Russia has a policy that it will not prosecute its citizens for computer crimes unless they perpetrated them against Russians or Russian organizations. My understanding is most ransomware has code to detect Russian computers (e.g. by checking localization settings), and will refuse to run if it finds itself on one for that reason.
https://krebsonsecurity.com/2021/05/try-this-one-weird-trick...
I don't know, I'm not a Russian in the ransomware business.
But I speculate that doing it that way might be so blatant and inconvenient to the Russian government that it might get the policy that protects them changed. Also, I'd imagine any bank that accepts such payments would quickly get itself blacklisted. This stuff isn't actually binary, so it's not smart to take it to the limit.