Bitcoin is useful for fast online payment. It is anonymous. It has very low fees and is very secure. It is a very universal currency. It can be used for charity works. It can make a digital society.
i agree with you that bitcoin has very lowest fees and no tax is apply on bitcoin because there is a lot of people invest their money in high amount in bitcoin and bitcoin is profitable currency if someone invest their money in bitcoin they get a good profit from bitcoin when price rise up.
That is a problem, profit! People are ready to do a lot of things for profit, good or bad, and thats why any currency will be used for good and for bad things, there is no exception in this matter. I think selling guns is not a good thing, but someone make a lot of profit on that, weapons, drugs, other illegal activities brings higher profit without taxes, then selling hot dogs, cars and real estates together.
That is a thing with profit, the ends justify the means.