How about this: we have three dachshunds, which added together don't equal a large lab, but we get three charges while the lab only gets one. In fact we almost were turned away from one park that has a two dog limit until I pointed out their size and promised to not walk more than two at a time.
Life's not fair!
BTW: we have a bag dispenser that clips right on a leash so we always have bags handy.