Here's hard numbers: Apple was responsible for more than 99% of all mobile app sales last year. cite: http://arstechnica.com/apple/news/2010/01/apple-responsible-...

So I don't think we can say "they just couldn't" — in fact, they just did.

And I might be skeptical about the numbers (Gartner isn't infallible), but every story I've heard from cross-platform mobile dev houses agrees with this — you'll get almost 100 times the sales on iPhone that you will on other platforms. I've never heard a contradictory story either, not even from Google trying to puff itself up. That's pretty much a monopoly.