You under estimate the power of cross chain transactions that aren't linked to any exchange.
Especially if the deal is done while in person where the correspondence of the trade is not recorded anywhere on the internet.
You are only thinking of yourself. Most people don't jump through hoops. They use a product and expect it to deliver what it promised as main feature.
If you can scare most of the people by attacking the low hanging fruit, society pisses on that coin forever after.
Edit: and as a developer, I don't want to be responsible for millions of people being subjected to State wrath some years from now.
You are asking me to be INTENTIONALLY cavalier, irresponsible and careless as a developer.