In fact, in our world there are no useless things as the creation of one technology leads to the creation of another and bitcoin is an example. Bitcoin start chain industry which is developing rapidly. I do not believe that bitcoin is useless.
Bitcoin in itself is useless as it represents the ownership of nothing. On the other hand, Bitcoin industry is not useless since it generates enormous profits for the exchanges, miners, developers, ICO teams, wallet providers, etc. All of them benefit greatly from the game where
greater fools transfer the ownership of nothing from one address to another. But this game will ultimately end as
you can fool some of the people all of the time, and all of the people some of the time, but you can not fool all of the people all of the time.