https://wccftech.com/apple-explains-why-microsofts-xcloud-is-not-on-app-store/

Apple has provided a statement to explain its stance on why Microsoft's xCloud and Google's Stadia cloud game streaming services are not available in the App Store for iPhone and iPad. In its statement, Apple has missed the point of why users and companies alike are publicly complaining, and instead, it has stuck to its old routine of talking about the App Store's benefits and features.

Microsoft publicly announced that it will not be bringing its xCloud streaming service to iOS and stopped testing early because Apple's App Store policies do not allow the service to work in its intended state.