When it comes to Bitcoin, privacy is a big deal to a lot of people, and it might be because they are partaking in a type of exchange that their government doesn't agree with. It also might be because certain Bitcoin-related businesses may blacklist you due to using gambling sites. This article is meant to give a few pointers on the various techniques of tumbling Bitcoin by sending satoshis through the laundry.
https://news.bitcoin.com/tumbling-bitcoins-guide-rinse-cycle/
Wow what a shitty article. Could have summed it up with buy BTC clearnet send to "darknet wallet"... and then use a tumbler.
Barrelrolling is not even mentioned.