There is this saying that you can force a horse to a river but can't force it to drink from the river and same also applies here in referral bonuses as you can get one to use a particular casino and also your referral code or link but might not get to deposit or even wager and most of the casino requires you to get those you refer to first register, make deposit and then wager before one could claim these bonuses and if you'll agree with me that isn't an easy task especially in a country like mine.
I do not use to refer people, just because I have read the terms and conditions that apply to referring people. You are right but this does not only apply to gambling. Recently a friend refer me to one of the common online banking in my country, if I do not deposit that day, he will not get the referral bonus, this is everywhere.
Referring depends from sites to sites, I mean the type of service an organization is referring. Example is on freebitco, which is a faucet (though a gambling site too), also are many other time wasting faucets like Cointiply that you can refer people to to claim forked coin, that kind of referral reward can be simple, but in referring in banks, gambling sites and many other sites that require humans to deposit before the company can gain or make money, the referral reward can be when the person referred has deposited and make use if the site already.