Most retail investors don't complain. And most brokerages settle before going to arbitration, because the win rates aren't great and either way it winds up on your record.

> I'm not talking about somebody doing some sort of complex options play

Those are actually more likely to go against the investor. Someone making an over-leveraged nonsense play is more sympathetic. (Or, investor was an idiot but broker failed to file a trade report on time or sent a stupid text or whatever.)

> Why should they get their money back?

Big question. Simpler: they do. A quarter to a third of cases between '21 and '26 resulted in customer awards, per your source.