Because the US monetary policy and inflation, and USD not being backed by anything, and because people don't want this power in corruptable governments.

This is not even some dispited facts (that this is one of major reasons for why some people want a new currency), this thing has been discussed over and over into oblivion, since the beginning of cryptocurrencies. It is a question that has been answered millions of times at this point. You just haven't researched any of it.