The thing I don't understand about mixing is that shouldn't it pretty much always be taken as an indication of money laundering? I can't think of any reason someone would need to mix / tumble coin if it were all legit.

Seems to me that receiving bitcoin from an address known for mixing should be an automatic red flag.

Financial privacy. You can still report it on your taxes. Maybe some of the coins you now own were stolen and you just happened to get them from the exchange and you are concerned about the fungability of bitcoin in your legal jurisdiction.

You might not want to paint a target on yourself by making known how much cryptocurrency you have, hence you'd like to keep it a secret.

You could say the same thing if you'd live in Sweden and with "normal" money: "Taking out money from the ATM should be automatic red flag, since no one uses fiat except criminals to buy drugs."

You might be running a business and not want to let your competitors know how much you are spending on advertising, R&D, and such like.

Doesn't really answer the Government's (legitimate IMO) question: "You just sold $25,000 of bitcoin on {US_Based_exchange}, where did it come from?" Mix it all you want, it wont save you from an IRS audit or other formal Government inquiry if they so choose.

Attempts to obfuscate sources of assets on a completely public blockchain could probably qualify as money laundering, in and of itself. Its not really much different than the cash -> casino chips -> cash launder (which gets reported to the government, or is supposed to).

It's a lot easier though. "I made it camming, here are the tx records". Or "they're donations to my project X". Or "people bought in to my last ICO". Sure you will need a bit more work than that, but Bitcoin makes it far easier to setup a ton of transactions coming to you.

Mixing is to Bitcoin as cash is to real money, except with Bitcoin nobody who doesn't have anything to hide uses mixing. It makes it easy to separate the criminals from the normal people. Sounds like a governments dream to me.