Facebook doesn't want to make it easy to revoke access to your data. They intentionally made it 3 clicks, just to make it more difficult. If it was super easy to revoke access to apps, developers might not be so interested in writing for their platform.
That, or the incomplete user experience is simply due to Facebook's motto of "Done is better than perfect." There are plenty of areas where the UI is lacking that have no affect on app developers.
