What is the benefit of having them as your referral if they withdraw the funds instantly after receiving the tip? The new users are required to fill the level 1 KYC information to enable the withdrawal on Stake. Although I could be wrong here, but Stake team may apply higher level KYC requirements on your referral if most of them just withdraw the funds after receiving the tip.
This is quite normal when someone try to give small bonus for anyone who is willing to register through a referral link. Free money hunters may try to abuse it by register as referral then they will withdraw once they receive the tip as promised. Of course it will be depending on the amount of the bonus, but free money hunters may do it even if the amount is small and even if they need to do higher level KYC process. For me, offering free money to register as our referral is effective to get number of referrals only but it wont be effective to get referral commission or to get real gamblers as referral.