How many successful apps require a pen or keyboard?

Microsoft Office and Google Drive would be the big ones. No one's paying $799 to watch Netflix when a $250 iPad will give them the exact same experience.

And notice that neither Microsoft, Google, nor Adobe sell “iPad apps”. They sell a subscription that allows you to use their apps across all platforms.

I've never paid for the app versions of Office or Drive and have used them for years. You can still use them across multiple platforms free of charge.