Creating a paid or ad-supported client app for a website isn’t profiting off of content, it’s profiting off of the user’s desire for a better mobile experience. There’s no ‘stealing’, the developer never has access to nor purports to own any of the content themselves.

That said, any client apps that run ads is dumb and will fail miserably. It’s awful for UX. Just so long as client apps can be monetized in other ways I think it’s fine to adopt a license that prohibits specifically ads.