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.
Usually, it is the job of the person viewing the link or advertisement on those sites, so they are the ones who have to check whether the casino is legit or a scam. But the problem is those people don't check it in more detail and are only interested in the promotions given by the casinos. The streamers will also be very careful in providing referral links to their followers and only provide casino sites that are truly trusted. The streamers don't want their reputation destroyed by misrepresenting their casino site.