Now suppose that the coins you decided to use had to be manufactured in an expensive process to prevent counterfeiting. When this became known 95 of the 100 people involved decided to not bother. As time passed more and more of them joined in and worked hard to create more and more coins.
Now some guy in the 20 who never bothered working for it decides it would be more fair if he gets a cut out of the work everyone else did "just because".
Right. He wouldn't want it if it had no value, as he assumed prior. Asking someone to give you wealth because you didn't know it would be worth something in the future is not fair at all. The argument that nobody will adopt the coin because people are wealthy (and presumably not spreading any wealth, which obviously means no one is adopting the coin) is just his misguided observation.