Claiming referral bonus is not generally a waste of time because, a good number of people have claimed bonus
from several gambling sites when they referred friends,it might not be an easy task though especially when people you share your referral link to ain't using it but also some sites would require a certain number of referrals for you to get your claims and in cases where you don't meet up the number of referrals needed to claim then it becomes a waste of time like you said, however I've also come across cases where people meet up their referral target and find it difficult to claim their rewards my advise to those set of people is that they should contact the customer support of the site and lay their complains so they'll see to it and get it resolved.
The websites or platforms that ask you to bring a certain number of referrals and then only you can claim any reward are nothing more but scams because a legit service would never give you a target when it comes to referrals but they simply compensate you for anyone you bring to them, so if you are using a casino platform and refer people to it, it should pay you the commission even if you have referred just one person.
Everyone should stay away from websites that promise very high returns or referral commissions and ask you to complete a specific target and then you can be eligible for rewards like referring 5 or 10 people first, these kinds of websites will only use you to get more visitors to run their ads and won't pay you a penny.