For me, affiliate or referral is very difficult to do because there are a lot of things that I need to do before I can get people to join under me. I have experience in the past to use affiliate to promote some products, and I don't make much money from the affiliate system. But I think for other people if they can find one method to work, they can focus on expanding and promoting it to other people.
It depends on how you promote the site/spreading the referral link. There are some people risking money for affiliate program by making website, offering free money for referrals, etc. Indeed it cant be considered as betting, but something like investment to gain referrals. Some other people do it for free by spreading the link on social media, forum, free blog, etc so it is obviously no risk at all.