Much higher rate of sales (apps and IAP) and subscriptions than Android. Not sure how the ad market looks (I've not worked on ad-supported apps) but wouldn't be surprised if those—at least in some categories—also pay so much higher that they're more lucrative on iOS, too, despite the smaller user-base.

Because people use iOS devices, and they want these apps.

The only reason we're talking about something as obscure as DOS is because it wasn't threatening. Now that people have raised awareness of the inconstency they're blocking it, like many other general purpose emulators.