Trading is a very smart job honestly because there are very very rare chances of occurring loss when you do trading because most of traders have stocks of bitcoin..
If the exchanges charge a fee, trading is a negative sum of game. The traders as a whole will lose money.
That would be true if the system were closed, and there were only traders present there, which it is not and there are not either. Though I agree that most lose money in the end which gets accumulated in fewer hands...
But the latter is irrelevant to you point and holds true in respect to any valuable resource