It helps towing a boat maybe, but if you have a wdh, you have to hitch it up without the bars first and drive it around the block before then adding the bars. So in that respect it does prolong the hitch up process for a travel trailer. If your wdh is setup correctly, you won't need additional load capacity. Now that being said, you can add the load leveling nivomat shocks if you get an expy without them, i believe it's around 500 to buy the parts, assemble the unit and install.
So people only tow boats or travel trailers with their Expeditions? What about 500lbs of sod in the back or 8 people in the truck or a family of fives luggage for a 2 week road trip vacation etc etc etc. It wouldn't help for any of those scenarios??? The positives of the LLS far outweigh the negatives.