The big difference between cryptocurrencies and other scams is that even the scamsters believe in it themselves.

There's a story that Heinlein describes, about a man who spreads a rumor that gold has been found in Hell. One at a time, and then in a rush, everyone leaves for Hell, until it's just the original guy, who says, "I guess there must be something in it after all," and then there are none.

(He incorrectly attributes it to Twain - perhaps Heinlein made it up.)

People are lost in the dream of something for nothing. How can you compete with a Fairy Godmother?