> number seems very small compared to the sheer number of retail investors that lose money on options and a lot of these don't even go in favor of the complaintant either

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.