Bitcoin is already heavily regulated if you want to commit a crime using it, hell you can scam people out of their crypto and be fine but if you scam governments and evade taxes using crypto you will be caught and that is why people won't be using crypto for illegal activities when there are easier methods.
banks have limitations when it comes to how much one could withdraw. different countries may have different laws regarding this but in my country we are only allowed to withdraw about less than $10K a day and banks will probably be alarmed when suddenly one person will withdraw such amount every day, probably even every month.
if someone don't want to raise suspicions he'd rather make it gradual stay stealth under the radar.