Is there a fundamental reason the world can't use one world currency?

1M Ago
The current world we live in has over 100 world currencies with maybe 5 "super power currencies." This seems to be the current equilibrium reached given the technological constraints. Constraints that led to multiple currencies: Geographic separation, different monetary policy based on local economy which leads to different levels of interest rates, local laws, others I can't think of. What I would argue is with bitcoin these historical constraints are not constraints anymore. And if that is the case, can the new equilibrium for the number of currencies in the world be 1? I am not saying moving to bitcoin as the one world currency any time soon. But in the long-term, say in 100 years, is it more likely there is 100s of currencies or just 1? Is there a reason the world needs more than 1 currency?