I agree with the sentiment of your post. However, on this trip the lady organizing it and myself were the only experienced backpackers in the group. Though during pre-trip planning I tried to advocate packing light, we were spread out throughout the country and were not able to do good shake-downs to reduce weight. I can't blame the other two (my girlfriend's gear was pretty light) for packing heavy. Neither one had been on a backcountry trip before and like most people do, they packed their fears. Throughout the trip I was able to give them a few pointers on how to cut their weight and hopefully they'll use their newfound knowledge on other trips.
More to the point, my entire logic for trying to reduce weight is to simply enjoy my time in the bush more. However, it's only one small aspect of increasing trip enjoyment. Another important aspect of increasing enjoyment, especially on group trips, is having everyone get along and keeping group morale high. In my mind, I'd much rather haul an extra 10 lbs of gear on my back than watch a 50 year old lady struggle up the side of a hill because she didn't have the time, money, resources, or knowledge to reduce her pack weight.
The one stipulation that I enforced on the trip was that I was happy carrying additional gear, but only food and other group stuff. I wasn't going to be hauling someone's heavy, inflatable seat pad so that they didn't have to sit on the hard ground at the end of the day...
That being said, despite my initial frustration with having to carry a bunch of extra gear, it rarely mattered when we were wandering around enjoying the marvelous views.