Basically we don't know the risk in every site if you invest money in a site first is you don't know if the site was trusted there are site that can give you small profit but many site are just scamming people who invested.
You are right,
no one can figure out which sites are right and which ones give little profit, even there are fake sites. but who knows if we do not try it. and I think all investments are definitely at risk, so we better not give up before trying.