Why are mixers legal? The only purpose I find on them is to money launder. They are literally useless if you don't have anything to hide.
The purpose is to obfuscate the trail, money launder is the bad/negative side of mixers.
Privacy is a matter in crypto world, let's say if you own huge amount Bitcoin and anyone know what's your name, your location, your home etc. You'll simply got attacked by $5 wrench attack.