The fact is that that there is no anything like money laundering but governments want to buy BTC, just assume that when you buy bitcoin then you use your credit card or bank account, your money already has transferred at that time to a foreign bank account and you have bitcoin in exchange with that, similarly if you are a miner who mines bitcoin then you sell bitcoin either in your country or either to someone who lives outside, then in exchange he transfers money using a bank account to your account so how it could be possible that money laundering might exist? Governments want to keep the price of Bitcoin down in order to buy more Bitcoin by spending the less amount of so called "Fiat" currency.