From what I've heard the IRS will hound any former US citizen and resident for taxes no matter their current location. You may not have to pay them, but you would still have to deal with them, so good luck with that 
They'll apparently hound you anywhere except Puerto Rico because it's exempted from federal income taxes for some reason.
Puerto Rico offers an unparalleled tax incentive: no federal personal income taxes, no capital gains tax and favorable business taxes all without having to renounce your American citizenship. For now, the local government seems receptive toward the crypto utopians; the governor will speak at their blockchain summit conference, called Puerto Crypto, in March.
Things might change if it gets exploited too much though. Not having to renounce your citizenship is a good thing but you'd still have to move, so it might not gain too much attention from US crypto people.
it's because they aren't a U.S. state. it's not as sweet as it sounds either. puerto rican residents still have to pay federal payroll taxes. if you're a self-employed trader/investor, that means 15.3% flat for medicare and social security. puerto ricans also pay income taxes---they just pay it to puerto rico instead of the federal government. they also pay 11% in sales taxes, significantly higher than any state in the USA.
if it were straight up 0% income taxes and sales tax weren't so high, i'm sure more people would move there.