The shortest answer to why Ponzi schemes will never end is because people always patronise, if after the few ones have been exposed, people decided not to ever join such things again there won't be any left today.
People like making money in the worst ways possible, anything that's easy money they will be lured and scammed, funny thing is they don't ever learn their lessons, when another Ponzi comes up again they will join..
I have no pity for people who like this way of making money, it's always like fetching water and pouring it all into a empty basket.
I agree that the demand for these schemes helps them to stay around, but I think you are too harsh when you say people don't always learn their lesson or that people should not sympathize with them. The thing is, most people who get involved in Ponzi schemes is not to make quick money. I'll say most of them join because they are being pressured, maybe they don't have any other better options or even because of incorrect information.
And secondly not everyone that involves in such schemes have ill intentions. Some actually believe that they have found a legitimate opportunity, especially if the offer is presented in a very convincing way or perhaps when they see that other people are saying that they "have made money from the platform" then they will drop their guard totally.
Sure, personal responsibility is very important but if we start saying "they deserve it", we are not solving the problem. The fact that these schemes keep happening is the problem, so I think awareness and education will help prevent these incidents, better than we always blaming people who fail victim.