Referral bonuses are just baits to win people over. In reality, its not what its actually presented as. The conditions are always vague until it gets to withdrawal, thats when you actually know whats at stake.
So they get gamblers in through those ref bonuses and promise them juicy offers and at the end of the day, you have to either commit funds or you are required to hit an almost impossible target to receive the ref bonuses in reality.
You are very correct, it is very controversial how referral bonuses are being promised to a customer if they refer people but at the end you find out that a particular condition is being attached to it as sometimes you might even find it difficult to meet up this conditions thereby not having access to your referral bonuses and often times if they give you access to this bonuses they will urge you to exhaust the whole bonus on a particular event which is very very annoying