It is business. Here in our place exchanges had been put to regulation and that will be subject for tax collection that will be passed on to the consumers. Aside from that another thing to consider is that bitcoin became a business and investmet to other users. The exchange does not earn in investing rather in selling and buying bitcoin. So, they are always winning and never loss money in this process. They just the one to process your oder (Selling and Buying) and they do not involve in holding btc.