There are dozens of privacy coins as XMR which can be used to conceal the transaction so I wonder why most people waste more fees on mixer to make their tranasction private. Converting your bitcoin to XMR before sending out is the same process as using a mixer.
I think people have their reason why they waste more fees to have a private transaction. My opinion about their reason is that they don't know that there is a service that can conceal a transaction that time or they are just being lazy to search a service that conceal a transaction or use XMR for example.