The time one wastes doing surveys can be spent doing a real job and earn real money which is like 100x more then what these sites give you , lol. Tis true human laziness drives such sites, they earn a lot out of the surveyers , and gain free advertising and hits through referrals.
Secondly if you actually want to earn through refferal links , I suggest you make a hit website and ask your visitors to click those links to support "funding for your awesome site". One of my seniors ran a tech site and he could provide credible answers to peoples queries regarding computer viruses which got him an awesome number of refferals.