It's not only a distribution fee. Someone had to develop the frameworks, the APIs, the OS and all the other systems that allows for your App to exist. These things aren't free and take resources to make and run. We can argue about the exact % but people often take all the work that goes behind the scene for granted. Same for Youtube and any other platform. We're just so used to having it all for free that we forget the sheer amount of work that goes into making and maintaining the platform.