If you violate the license agreement from apple there's potential for legal repercussions, and when you are trying to make money from their distribution channel (app store) it's generally better to not violate any of their rules. Especially since they don't have to give you much of a reason when rejecting or retracting your app from their store.

> I'm talking about why anyone not Apple should care.

Because otherwise they're violating the terms of the license agreement which means at best they get no support and are 100% on the hook for anything breaking and at worst they're at risk of legal action?

Building a hackintosh in your bedroom is one thing, violating the license agreement of the tools you're using to do your job is another.