You made the claim that that's the only reason people buy bitcoins.  I'm suggesting that for the vast majority of the world's population that's also the only reason they buy most other currencies.  So, if the claim that the only reason most people buy bitcoins is to sell them to other buyers is a criticism of bitcoin, then, if a similar situation obtains for dollars it should count against dollars in the same way.  It seems that the only reason most people buy dollars is to sell them to other buyers.  I'm certain this is true for me.  I'm just a sure it's true for my wife, and I'm quite confident no other reasons (e.g. that dollars had the advantage that they were already a very widely accepted money before their commodity backing was removed) enter into the minds of any of my friends.  Can anyone else speak to this?  Facts about the history of dollars may make dollars more stable compared to bitcoins, but what I'm saying is that those facts don't enter into the minds of most people as reasons they buy dollars.  What is in the minds of most people, I suggest, is that they can sell those dollars to other buyers.