The higher your status is, the more bonuses you get. For example, VIP players get weekly 100% deposit bonus.
No one will be interested to be your VIP players just because of the weekly 100% bonus since there is a 35x wagering requirement of the bonus. We can see this in almost all casinos with deposit bonus without the need to be VIP players. I think you need to give a better offer for your VIP users, something which can be used freely without any requirement.