It's because you're making regular payments for something that will eventually break down beyond repair, and will break down faster because your needs are geographically distributed and you're probably traveling for pleasure frequently. It will probably break down before you're even close to paying off the loan, getting you in trouble. Moreover, you need to make permanent modifications to the interior of the vehicle to live in it comfortably, such as removing seats, so you're destroying the resale value. The types of vehicles remotely suitable for living in are very expensive, full size vans and pickups are significantly more expensive than commuter sedans for a given year and mileage. Imagine burning through a 20K used van every 2-3 years, getting no trade-in value, lumping the remaining loan balance into another loan (if they even let you) and getting deeper and deeper into debt, as well as suffering all the psychological stress of constant expensive repair bills for shitty Ford/Chevy vans/trucks that could steal over 2000$ from you in a single state inspection without warning.

If you want to live off the grid, save money, and enjoy a high degree of freedom and leisure on low income, the only way you can do that is to live in a tent and drive only inexpensive commuter vehicles without modifying them. You'll probably still rack of mileage but it won't be a big of a deal. You could still get 4 year loans and get enough trade in value to pay off the loan balance after like three years and just get a new car without growing debt. Repairs for a Japanese car with 30k miles over the course of 3-4 years will be very reasonable. The only downside is that you need to work close to a national forest that allows camping and may need to move every two weeks.

Whenever I see picrel, I just see a financial ticking time bomb that will eventually cost the owner just as much as if he had just paid the inflated rent prices in the city he works and drove a civic instead.