I regularly shop at three different grocery chain stores. It's way easier for customers to switch between them compared to being locked into the Apple app store.
https://en.wikipedia.org/wiki/United_States_v._Microsoft_Cor....
You can buy/sell it on eBay. Or next upgrade cycle change brands.
Music that you bought from iTunes has been DRM free for ages.
Most movies purchased from iTunes are transferable to Google Play, Amazon Video and Vudu vis the Movies Anywhere app.