I agree. Mixing coins is not just for hiding illegality. If I have 500 BTC at address A, and send 10 to B my hot wallet for my vacation (or to buy a Starbucks or some tequila) C will not be certain that I own A. With pattern analysis however C can become more confident that I do and then your net BTC worth becomes much more public and you become a target.
Sure, you have a certain degree of anonymity if you are only buying online VPN services, but as soon as you purchase anything offline, you are tying one address and its chain of antecedents to you which drops your anonymity significantly. With a usage pattern available, it becomes more troublesome.
If I were Satoshi and wished to remain anonymous, I would be holding my coins until they are p2p mixing services established and well used prior to moving coins or he would be outed quite quickly. (Non-p2p are okay, but logs are kept and you are relying on a third party to be honest and not monitored.)
Cooperative unmixing is only really voluntary if the people participating in the unmixing are anonymous. Otherwise you have known and non-anonymous individuals facing the charge of obstructing a police investigation. Though I will grant that it has the possibility of delaying investigations through multiple jurisdictions, not unlike the Tor model. Tor however is always pretty clear that participants are expected to not maintain logs, for a reason. So the question is why do we want to move away from that model? You have to ask what is so different about finance verses information that we suddenly give up our resolve to allow people freedom.
No-one talks about co-operative unmasking for Tor operators "just in case" we want to trace a crime committed over Tor that the community can agree on.