Would be interesting to know the thought process for doing this.
Something like that I'd guess.
This was also in the first month of the App Store. iirc Jobs was nervous about third party apps being lower quality and tainting the perception of the platform, I don't think there was any PR calculus where this app survived
I refuse to use apps like this. None of my Apple IDs have payment information associated with them.
It does seem like quite a reach but I think there are a few legitimate niche markets for that price point.
Comparatively, a high-profile client spending tens of thousands of dollars in ads isn't doing so on impulse, they're doing it cause it's their job. They'll open up a browser and punch in some banking details if it's the only way to get those ads out.
Even if it were just for iOS and iPadOS though, they do want iPad Pro to compete with desktops in places where expensive software runs. For instance, Grass Valley Livetouch could be done on an iPad.