When people, businesses and banks start hording tokens instead of investing in building and maintaining the production capacity of consumables, the ratio of value of tokens meant to buy consumables vs the actual production of consumables gets out of wack.
When the music stops, people realize that others are sitting on tons of seemingly valuable tokens but stuff to buy with them is getting scarce because capacity is not being maintained, they reverse their trade, prices of stuff go up, volatility ensues in an incredibly destructive cycle.
Too much savings being tied to tokens instead of assets that create real value is an economy wide coordination failure, a terrible Nash equilibrium. It can be hard to solve because it's a prisoner's dilemma where the first people to invest in real production are disadvantaged so everyone hoards tokens instead.
This is what central banks are designed to prevent. We don't want cryptocoins to cause another great depression like gold tied currencies did almost a hundred years ago.