The reason for that is that the concept of 'Freigeld' forces people to think about production and consumption schedules. With regular money you can pretend that labor can be stored like any commodity, which is actually not possible.
"Capitalism and not participating in Ponzi schemes don't go hand in hand with each other" becomes nonsense. The last one to jump off that track before it collapses becomes capitalistic winner. But the ones who jumped before that moment are still better on than ones who ended up paying to them.