Here's the issue with mixers: they don't work. There have been multiple studies in the past showing that through simple, automated analytics, you can still track 99%+ of the mixed inputs/outputs and tell where they ended up. Remember, BTC is pseudo-anonymous, not anonymous. All you're doing is adding in a new layer of obfuscation but anyone could break that at any time.
If you make use of a manual fee in combination with a certain delay, plus the fact that you can have that 0.5BTC sent into smaller fractions to the destination addresses, it will practically be impossible to trace them.
But yes, there is absolutely nothing that guarantees you that no one will be able to spot them. But it's giving people a safer feeling. Especially when they send the mixed coins to their cold wallets.
There are always going to be ways to trace them. And the fundamentals of doing so are ridiculously easy due to how propagation works. I'm not saying it does NOTHING to obfuscate things, but those who are mixing are usually doing so for a reason. And mixing is not going to magically make whatever it is they're doing safe.