I’ll add myself to the list of people finding this the most interesting part of the thread. So what’s on the list? Are all of them effectively self-sufficient even though they’re walking in groups (to a campsite)
Almost. If you’re sharing a 2-man tent then you need to pack the tent up and carry it between you and your tent-mate. You also need to carry your camping stove, food, mess tins, clothes, toiletries, first aid stuff, map, compass, etc. Pretty much the only thing you don’t carry is two or three days worth of water.
At the end of the day you’ll probably be back at the campsite you started from where you’ll set your tent up again for the night.
As said, it’s often cheap (or cheap, borrowed) kit, which is heavy and bulky. But not many parents are going to spend thousands kitting out their kids in fancy goretex jackets that won’t fit them in 6 months time, or lightweight Ti camping stoves that will never get used again. And then you’ve got people who’ve never done anything like this before who are trying to gauge how much food they’ll need, and will usually deliberately overdo it than risk ending up hungry on the last night.