The only reason why people buy bitcoin, is to make money.
Wrong.
People buy bitcoin trying to make money. But there are two kinds of buyers, the ones who make money and the ones who lose money. Tons of people end losing money just trying to make money. But that doesn't mean bitcoin is a losing game. At the end, the ones who play it smart are the ones who end making money.
Trading is zero-sum game except broker fees and commission. Your profit is loss of someone else and your loss is also transferred to balance of other smart trader. Considering the facts about failure rate on trading it is obvious why there are so many exchanges,brokers,market makers than required.