So how would stopping people from making web video chat apps but allowing them to make apps that integrate with the dialer and phone history help them sell more devices?

They want a robust third party ecosystem.

Devoting developer resources to building/extending native iOS apps to integrate with iOS-specific dialer/phone history increases costs and extends lock-in. Web apps that can perform all the functionality of native apps, such as video chat and games, erode the value of the App Store.

Integrating with the iOS dialer and phone history means not implementing something else that would provide value across platforms.

The attitude that a company shouldn’t actually build features that are better for the consumer and instead are better for the developer is how we end up with crappy resource intensive, battery draining electron apps. If you can’t make an app that is in the best interest of the customer, maybe your product doesn’t deserve to exist.