Shaving grams is all about cool factor. All the performance testing results point to no important difference between bikes that weigh a few pounds apart for normal bike missions. The goal is to carry less gear and remain comfortable on the trip.
+1.
On the other hand the fact there are more important sources of efficiency only matters if the are mutually exclusive.
Also, 5 pounds can mater a lot when you end up having to clean and jerk your rig over a concrete divider, particularly if you weigh 100 pounds to start.
And cycling is a great alternative for people with limitations... Get back to me when you are 60.
If you are riding fast enough aerodynamics is more important and rolling resistance of your tires matters a ton at slower speeds.
Another big +1. Does this mean the 4" tires no longer roll just as nicely as the 1.5" ones?