That seems like a business decision. Not a clinical "obsession". I suppose Apple's business decision could fail (some of them have), but if you're saying that Apple's default apps decision is a failure, reality disagrees with you so far.Because it is an obsession with apple. For years they didn't even allow you to remove stock apps from your list of apps on your phone. You still can't change the default apps on iOS... you've been able to do this on every other mobile or non mobile OS for absolutely any piece of software since forever, but not on iOS, but have to have mail and safari set as default.
I really think it just puts more people off when you try to force people to use something, that strategy just doesn't work. It's failed for other companies... just look when xbox tried to force people into using kinect when the xbox one first came out. Yeah that worked well.