What is the reason why people should use mixers (if they for example want do launder btc)? Never used such services but for me it seems better just buy some forks on exchange and buy bitcoins back. At least you won't get even dirtier coins than you had before.
If you use an exchange, there is a trail. Most exchanges require identity proof, especially if you trade large amounts. Mixers have no such requirements and can tumble your coins for a small fee.
Boom. Here is your answer, right off the bat. Good job.