Actually it has nothing to do with competitive platforms for developers. All that matters is that Android and iOS compete with each other, which they do tremend

Actually it has nothing to do with competitive platforms for developers. All that matters is that Android and iOS compete with each other, which they do tremendously. From a developer standpoint, they simply decide to start a business or not, knowing the expenses of doing so. Whether you are a new company, or any existing one like Twitter, you can do the math. Look at the costs and ROI. It is worth noting the platform fees have never gone up, only down.