>  but retaliation is a thing, and is hard -- and expensive -- to prove.

My understanding is that it is fairly easy to prove. If you suddenly have a change in working conditions it is considered retaliation. See the example here[0]. Doesn't matter if you're in an at will employment state. If you get terminated really close to a reporting, well, you'll probably take home more money than you would have by working. It's up to the employer to prove the termination was rightful and they can't just say "because".

It also is not expensive. At least not more than the theft. Lawyers working on wage theft generally take payment as part of the recovery. You pay out of the winnings, not up front.

Honestly, a big part of the problem is that many people have defeatist attitudes. A lot of people don't even bother to make a report after they leave. It is hard to retaliate when you've left.

[0] https://www.dol.gov/agencies/whd/retaliation