In some part I agree with you., but that's now. In the near future more and more services and apps will have an API as a primary way to be accessed by third party developers.

Don't know if that will be your need since all depend from the service itself if it is useful or not. But we have to bear in mind that Twitter has 75% of its traffic coming from its APIs, while eBay has 8 billion of worth items pushed through the marketplace via APIs. That's the future, especially when the internet of things will come, at that point your toaster will have an API as well.