If they get big enough to justify a bigger more diverse dev team I'm sure they'll get around to a web version as well if they can deliver the same experience on web.
I'm building an app, and being able to deliver a better experience when selecting an image/video to upload was a consideration and one reason why I didn't use a mobile site and instead went with an app.
Push notifications are another big appeal of apps vs. a website, although I know that has changed somewhat recently it probably won't cause any massive shift in mobile site development.
Oh, and tracking :)
