They can get pretty heavy if they're not dry, and there's likely to be grass in there as well. Dragging is way more strain on the machine than pulling something on wheels.
#5
ILENGINE
From my research it looks like that bag full could be 450-500 pounds
#6
Scrubcadet10
I use the mule to haul the tarps of leaves out to the burn pile, if it's light enough i can throw them in the bed, but sometimes a bunch of wet leaves add up quick, that's when the 900 pound towing capacity comes into play