Don't be so hard on people.
Say you're horribly out of shape- no strength, no cardio, overweight, skinny, bad knees, whatever.
Let's say your physical condition is such that hiking only 4 miles with a 30 pound pack is all you can handle in a day.
Wouldn't carrying a 15 pound pack possibly enable you to hike 6 or 8 miles instead, thus creating a gain in your personal performance?
Sure, everyone should try and get in great shape; you'll have a better, longer life.
But that doesn't negate the benefits of a lighter pack.
It's all relative.