I’ll rise.
Put it this way, I’ve lost weight, and gained weight – I know that I’d rather carry an extra stone of fat, than have a bike that weighs a stone more. Ergo, the weight on my back is less noticeable than the weight I’m trying to hop up and over obstacles.
Your back and leg muscles bare the brunt of a back pack more effeiciently than your arms and stomach muscles would need to if all the weight is down low.
Would you rather carry a new born baby around in a (baby friendly) back pack style holder, or out in front of your knees?
And bunny hopping, manuals, wheelies, clearing gap jumps – prefer to lift the weight with your back/legs, or lift a heavier bike?
It’s not about stuff being lighter in a back pack, it’s about a more dynamic distribution. But hey ho, different strokes.