It all comes down to supply and demand, which is the basic law of any business. Exchanges don't pop up because they want to do the community a favor, but because they know there is a market to serve. Markets consist of people, and these people vote with their money and coins and basically beg for more variety in the exchange space.
I personally couldn't care less about the profits Coinbase has booked when that money is being pumped into shitty token promotions and not in the one and only coin that allowed them to grow out to the worldwide crypto phenomenon that they are today. They don't even pump any money in providing their customers a swift support experience. Absolutely pathetic.