Referral programs can be very profitable but it's not for everyone. This is why you see many gamblers complaining about not making any profit from it.
As for those that has deemed it fit for chasing after referral bonus, they don't actually mind about the numbers of gamblers they send referrals to because they believe out of twenty that received the invite through them, atleast 8 will show interest, but sometimes it a whole risk of a thing because it seclude you from your privacy, you have to be hunting for people to refer all because of what you want to get as referral bonus and everyone knows you as a gambler.
I think the number of persons that you send your links matters as much as the type of persons you send your links to and just as dunamisx said about sending tye links to several person and hoping that 20 percent of the persons the link was sent and possibly 5 percentage of the 20 percent might also click on the link and accept to use the link and no matter the amount deposited, there will be a profit for the referer.
I still stand on the ground that referral bonuses aren't easy to claim and wasn't for everyone and from my point of view, I really don't think the referral bonuses aren't worth it especially for the common man except for influencers
If you have a blog or site, you can do the same thing or better still a YouTube channel with large numbers of audiences to communicate with. This is how so many YouTube influencers had been getting huge referral bonuses because they can influence people to use a particular site to bet and eaen bonus.