How would it be possible to track back to the origin source if the transactions were mixed, broken down and distributed across random intervals- all to different addresses?
Realistically it's pretty low % of you being trace back to those coins, but the main problem with the mixing method is is ultimately centralized, you have to trust that the mixer service will not keep logs and deliver logs to authorities or someone else if requested, let alone owners of the mixer service taking advantage of the logs for blackmailing and whatnot. That's extremely paranoid tho, if you aren't moving ridiculous amounts of money and you just want to move a couple hundred around no one is going to care.