Casino platforms typically allow affiliates mainly to grow their business. A person just referred and earn is not possible in casino platforms. As you said everyone will have wagering requirements as well as their minimum deposit amount. There may also be other requirements. A person is eligible for referral bonus only if all those conditions are successfully fulfilled. Affiliates can easily gear up a person's earnings but referring without the terms will only be considered a waste of time.
Yes, you are right and that is why they offer the highest commission for their affiliate members. They do encourage it with special offers assigned to the affiliate link. A high converting affiliate would also get personalized offers and would be assigned an affiliate manager. I have seen quite a few good influencers. The commission depends a lot on how much deposit it a referee did and how many times wagering was done. The money through affiliate commission is quite good but it does require a system to generate such income.