I don't think that anything should be taxed. I think that once you buy something (House, car, TV, etc.) it should be yours and they shouldn't be able to collect taxes on it.
They shouldn't be able to tax your wages, or your capital income, or your Cryptocurrency, but they do, because everyone surrenders it to them.
Now, I think the government should decentralize it's taxing authority and mine crypto for it's own uses, but they won't, because it's easier to steal other people's money than earn their own.