dont need to think twice cause every ponzi uses this trick to get money. But still they are few people who fall on this scam ponzis those who are desperate.
Because greediness is the main problem of people. Everyone wants to buy a legal money printing machine for a few dollars. The best example is bitconnect that stole astronomical amount of money from greedy people. It was a clear ponzi scam, but a lot of people still invested in it, despite many warnings ! Some of them even sold houses for investing in that shit. That is a clear sign of greediness and stupidity of people who wants to became rich by doing nothing.