because people want to produce without doing anything, it has become a natural phenomenon, where you only spend a little money to multiply it, let's say 1 person sends 100 $ if 100 people then it becomes 10000 $, they are interested in big profits.
Those people are actually the ones who aren't well informed or educated regarding investing. As an investor, you should keep in mind that there is no such thing as fixed in return to what you've invested. If there is, it should be provided by the banks and if not then it's 99% scam. These investors are also being blinded due to the influence of the people that surrounds them. Unfortunately they trust easily that's why they don't tend to do a research for themselves.