Used them for wet gear, mostly up the center-back, but with a short length of bungie you can run vertical things (tripods, hiking sticks, whatever) if on the sides.
Also used them for wet crampon bags (drip drip drip) and for lashing snowshoes with.
If you have on both sides, you can can get a length of elastic cordage at a sewing store and a cross it up across the back to make a spider web pouch.
Wouldn't say they're useless by any means, but they do allow for some creativity.
Cheers,
-mox