Those programs are tools for cheap advertising models. If we join them we are voluntarily exposure ourselves to advertisement. business people use conversion rate to estimate profits. since this model of business is very cheap to start, a lot of people are using this model. when they got some profit they stop this one and then start a new one. The reason is because new venture is very likely to promote by affiliate. So as long as they are people willing to promote them for free they will continue to flourish.