So many things are easier to do on an iPhone. For a lot of things, it’s easier to do business via a small app than the company’s main website. Companies get excited and (correctly) are happy with a great app interface.
But there’s a bigger lesson (and opportunity): Maybe your app seems so great because your website sucks. If you can do the job with a few small screens, maybe all the other crap on your website is just clutter, distraction, and interference.
Lesson: Use your mobile site as a new standard by which to reevaluate your main site. Figure out what you can simplify. Figure out what you can eliminate.