People don't like change (variation from the way things have always been), especially if it involves learning about or getting used to something new. In America the legislators are still slightly afraid of the voters. In foreign countries people just accept it when the government tells them a change is for the best.
Evidently there's also not a lot of lobbying money behind making sensible changes to coinage.
I guess what your saying is that there is no campaign cash out there for a politician to make for changing paper dollars to coins.
Follow the money takes on a whole new meaning.