With a peep and pin arrangement, you've got a long sight radius for the best aiming precision possible. With these types of 'rifle' sights (actually more like pistol sights, if you ask me), you wind up with a short sight radius. It'd be like mounting the rear sight on your rifle 6" behind the front sight. Does itmake any freakin' sense to do that? NO.

Doesn't make sense to do it on a bow either, to my mind.