I'm not sure you've done enough macOS/iOS development to know where that feeling comes from. In every Apple developer conference, in much of the UI API, and in input from the community, the idea of creating beautiful apps is something that gets repeated over and over until it is ingrained in us. It has nothing to do with trying to be better looking than other platforms but rather trying to match the aesthetics and quality of other apps on the same platform. People tend to notice when your one utility app stands out as the ugly duckling on macOS/iOS.