The pattern is because they're the exact same app. All of those are just the iTunes Store, which is a web page on every platform. The iTunes Store is a little clunky but it works fine.
Apple also have the Apple Store, which is a separate thing that's a website - I believe it's a WebObjects app and the iTunes Store is as well.
The saddest part about this is that using WebViews really doesn't have to mean that it's clunky and slow. Slack's interface is pure HTML, CSS and JavaScript and it works just fine.
Apple also have the Apple Store, which is a separate thing that's a website - I believe it's a WebObjects app and the iTunes Store is as well.