As far as I know they are just for attaching more gear to your pack. I hear tell more specifically for climbing gear like cam's, carabiners, quick draws etc.

I do a lot of backpacking and can honestly say I hardly ever see them being used. When I have seen them used it is only for attaching more gear to the outside of the pack.

Because they appear on all size packs. Much larger than you would use for rock climbing. I will go out on a limb and say manufacturers sew them on so consumers "feel" "cool" with the extra doo-dads on there pack.

This has been a long time question for me as well so if I am wrong and they really do have a specific purpose. I would love to know. I will need to hurry up and go get the specific item that I have obviously overlooked and am in dire need of and have overlooked. My gosh I hope I haven?t been doing this whole backpacking thing wrong.

Thanks
Cameron