I still use the same external frame I did as a Scout, and our ten year old uses a Kelty external... This summer, he climbed 3200' over 9.2 miles from trailhead to first camp with that pack, carrying all his own gear. I can tell you that, were he (or I) carrying the type of gear I did as a kid (uphill in the snow, barefoot and grateful, yeah), it would have been a death march. Due to the reasonable weight of his gear, he was able to include a fishing rig, some cool stuff and still roll right along.
Ultralight is particularly suited, to an extent, for youth such as Scouts. They benefit from the weight savings and can take advantage of things older, larger folks cannot -- that Cosmic sleeping bag is an example: my son uses the "short" version that I don't even fit in, and saves weight. He also uses a foam pad instead of an air pad, like mine, and has a mess kit that weighs less than half what the Scout kit did before he modified it, w/o loss of utility. Heck, if we went full "bag meal", he'd be down to a spoon and cup!