I think that has more to do with how utterly mired in old software and hardware the business sector is than how good Apple would be as a replacement.
Speaking from experience, the corporate sector is notoriously horrible at moving forward.
And I think relegating Apple to "toy maker" is a huge mistake. They don't have the luxury of already having everyone sucked in. Their partnership with IBM has been a wild success from what I've heard and read. It takes time, but I wouldn't be surprised to see Apple's enterprise market share continue to grow.
You underestimate their mobile footprint in enterprise.
Apple doesn't - to date - offer anything to replace these antiquated systems though. So there you go...