Hey tokeweed, I'm hearing you out! Here's my take on it, after seeing several discussions and thinking about it myself.
1. To launder that much money, you'd have to be moving a LOT of bitcoins. Regularly. If the total market cap of crypto is only 165 billion, and of that only 94 billion, we're talking about very noticeable amounts being laundered. Even taking into account a $5000 Bitcoin value, to move 1 million dollars requires 200 Bitcoins. And we know the industry is moving hundreds of millions a month. Those Bitcoin volumes moving into USB wallets are going to be very easy to detect. Getting someone to SELL you those Bitcoins is going to be hard to find. Exchanges as we know them are going to be very difficult as well.
See, if you're moving millions of fiat in a global market of 100s of trillions, it's a speck. Perhaps when Bitcoin is valued at 100,000, it may become more viable.
2. It didn't take long for the FBI to track down dark markets who went through the trouble of mixing, remixing and anonymising their transactions... on a volume far smaller than drug cartels. What this tells us is that the tracking software has become very sophisticated.
I believe the technical knowledge required to hide and launder Bitcoin, being a non-anonymous public ledger and all that, is a deterrent to major organised crime to using crypto. They've got great accountants schooled in conventional finance, but not yet the skilled programmers who would help them use crypto to their needs.
However, due to ETH's architectural difference (and Monero's), illegal activities are moving towards them and it may well be that they could be used chiefly for these. Research already shows Bitcoin illegal use dropping sharply, and is predicted to be less than 5% of volume end of this year.
3. Most likely, they haven't heard about Bitcoin yet or don't know yet how to use it. Somewhat related to (2)... but you know, these guys are probably unimaginably removed from our world of computers and digital tech. Call it a deeply-ingrained culture of paranoia!
This is a very good explanation.
Indeed, trade in illicit goods was a driver of bitcoin price a while ago (at the times of Silk Road, where you had to have btc to trade), now it is negligible.