Most casinos count only $20 if you wager a hundred dollars. We cannot blame the casinos for that because they wrote it somewhere on their TOS page. Since people do not read the rules carefully, they should be blamed instead.
ToS is TLTR, but it is written for fundamental terms of a company for users. For details like wager conditions, I believe they are not written in ToS but in a specific promotion program, or tournament.
Users need to read Rules & Conditions of a specific promotion program or a tournament, before joining. They have no reason to blame on the company, because they are lazy and don't read Rules and Conditions of a program or tournament.