People seem to be missing the point about Siri. When compared to the free app released two years ago, it's been neutered.
Where's OpenTable? StubHub? TaxiMagic? We've seen WolframAlpha and Yelp, but that's it. Wikipedia still has a full list. I count 19 services. https://secure.wikimedia.org/wikipedia/en/wiki/Siri_%28softw...
Siri promised to organize not just your phone, but the world outside your phone. Apple has integrated first-party apps beautifully, but heard not a peep about third-party services. Neither web services nor native apps can disclose their offerings to Siri.
The easy answer is that Apple doesn't want Siri competing with their app market.
I don't think it's so simple, and I don't think Apple is so short-sighted. After all, if someone's going to make your business obsolete, you want it to be you. Everyone and their grandmother has an app store now. What makes Apple's store distinctive is not only the quality of the apps, but the depth of the apps. Fart apps are obviously shallow (they're semantically non-existent), but a native port of a web service is pretty shallow too. How many verbs are required to interface with craigslist? How many kinds of nouns exist on Yelp? These apps have the capacity to be supplanted by Siri integration, but Apple missed the boat.
I'm comforted by Apple's admission that this is "beta" software. iOS didn't ship with any SDK (despite the obvious potential), and the reason turned out to be as innocuous as "it wasn't ready."
We've glimpsed the post-app world. Don't mess it up, Apple.