Those must be scam casinos. If people, like streamers, promote a casino for free, not paying them is considered a scam. Therefore, it is highly advisable to avoid such casinos. Referring others to a casino is typically not an easy task. It also affects your reputation when you recommend someone to a particular website. So, be mindful of the casino you're directing your peers to.
You're right, if one must refer someone to a casino, then he must have gotten some oast experience in dealing with them than making a recommendation on what will tilt your own reputation you're having with those you're referring, it is true that so many casinos are rewarding for referal bonuses while some are just a pool of tricks to get traffic and not maintaining their promise for reward, we should have a good understanding of what we are promoting, those we are introducing into the promotional efforts and the possible risk that may comes in.