The idea is that you never trade with the same person/entity twice, and you do so via means that obfuscate as much of your information as possible. 
Example, you may hate paypal, or revolut, etc but the only thing the person at the other end gets is a username.
Meanwhile paypal or revolut have no clue what the TX was about. 

So you decentralise risk.

With CEXs, they know your details (they see it coming from whichever bank details you give them), and they know exactly for what purpose. To 

That's the difference. It may never be used against you, but we know the direction things are headed, and if it comes to pass, CEXs are like a honeypot of information and have no choice but to comply (WoS literally left the US market recently because of this. Good on them, but it can only do this so many times, and few companies would be willing to leave a market as big as the US).