Sure, I used to use it. I won't explain the strategy, but I have a crypto trading bot that sometimes profits at the expense of other bots. The owners of these bots got so annoyed at this that they would blacklist the address at which my bot was, and would then track any addresses that I sent funds to from there and blacklist those in advance. TC broke this ownership chain, so they could no longer preemptively blacklist the addresses my bot operated from.

Couldn't you just deposit ETH in an exchange and then send it to a fresh address? Seems like a hassle to use TC for that specific use case.

Technically? Yes. But you run the risk of getting your account closed for this kind of thing.

And take on a bit more custodial risk

Privacy - just the general desire to participate in crypto as if it were cash, like originally intended. Right now if you aren't running a miner, you've lost that ability without tumblers.

Anonymity and privacy is very useful in a lot of legal use cases. One example is buying domain name without disclosing who is buying (disclosing that information may dramatically inflate price).

There are obviously workarounds without tornado cash but tornado cash is probably the cheapest option.