It would draw way too much aggro for little gain without any "legitimate usage" traffic to draw any substantial objections to shutting it down regardless of any technicalities be they technical or legal. Fund ingress and exit points are fundamentally a weakness for any form of "stealth" money transfer, even cryptocurrency if they are to actually be spent on anything material. Spies have been busted by spending their bribes as clearly beyond their means even if they overextended lines of credit when they were specifically not to because of worries of compromise. Otherwise it is a big risk for nothing and well - if you are willing and able to get away with murder without getting paid why aren't you a successful serial killer already or taking risks by taking requests if you are?

Neat little cyberpunk device but doesn't quite work in reality without some other foundational assumption changes for things like "actually somehow provides substansially better life insurance even if it may also be used to place a hit on you".

They are, it's called life insurance.

Because people don't kill for money. Accounting pays more.

Easier to convince people who have a death wish / create terror on people rather than death.

Poisonous animals generally don't kill, even when they are about to die. It's the terror.