There are reasons to weigh them. For example, for Bonnaroo last weekend I rolled 29 joints, and I didn't want to travel with more than an ounce, so I weighed the joints, then added some bud until I was just below an ounce in weight, just in case I got busted. At the end of Bonnaroo I gave a friend my remaining bud (the joints were all gone), so that on the return journey I had nothing at all. (Friend left the bud I gave him in a porta-potty by accident, so some lucky person found some really primo stuff. And since my friend was stoned enough to do that, I guess he didn't really need that bud anyway. Heh.)