I have a garage and a shed (OK, fine, it's a 24x36 barn) and a basement and a home office that barely contain the enormous quantity of my stuff at home. And yet I honestly think the highlight of this summer was waking up to the sunrise on one of the remotest parts of the Appalachian trail through the Great Smoky Mountains National Park, with no possessions that wouldn't fit in a 22L ultralight backpack - including several of the same items as this guy's kit.
On the one hand, most of the stuff is replaceable, "fungible" if you like, rather than sentimental. On the other, I keep it because I like to have certain capabilities, like cooking and auto repair and home building - I can't fit a tablesaw or pressure washer or food processor in a backpack; I've got a rack of 24 giant totes in the garage with painting supplies and plumbing supplies and bike parts and specialty auto repair tool cases and on and on that each occupy more volume than the one backpack this guy lives out of. I also recognize that this is a colossally inefficient way to allocate things among a group of people: I'm not going to pay a painter $1500 to do a crappy job to repaint my bathroom when I can do it myself with far greater quality for $100 in paint and a couple hundred bucks worth of tools in a giant tote, and neither are most of my neighbors, but this means that a sizeable fraction of people in the neighborhood live around our own personal totes of painting supplies.
If I was going to pay someone else to build and repair and maintain and clean the house/apartment/condo/hotel that I live in (when I'm not in a tent, that's only about 5% of my time), and to take care of the cars and bikes that I ride in and on, and to cook the variety of food that I eat, and on and on, I would have a lot less stuff. If I bought tools to do these tasks that I would use once and then sell/give/throw them away...that would be unaffordable for me. One of the lessons that my Dad passed down to me is to never buy a thing unless you have the resources in time, price of consumables, tools, and space to clean it, maintain it, fix it, and store it - those are real costs beyond the sticker price of a new toy.
Where does the money come from that allows one to sleep in hotels, ride in rental cars, travel in airports, and eat in restaurants for years on end?
