alt Hacker News>Courts, law enforcement and contract law.
That's the wrong answer. The existence of tokens predates the existence of government. It's the next step after barter. The correct answer is reputation. A vendor who cheats his customers builds up a bad reputation, and the only way he can keep doing it is by changing customer bases, for example by moving to a different town. Think of the traveling snake oil salesman who moves on once people realize his remedies don't work.
The courts etc are there so we don’t have to create a posse and ride out to find the snake oil salesman. You _can_ have commerce without them but it’s much higher friction. So if a crypto wants me to abandon the existing systems it needs to show it creates less friction.