I haven't used 4 bags. But I also haven't gone on a cross country trek.
As foreign more people don't do it, I would guess it's due tonight and fear of the 'what if'.
- Ultra light equipment costs considerably more than basic gear and a lot more than lightweight gear.
- the boyscout motto of 'always be prepared' hits home for many(most) when they are packing for an adventure such as an unsupported cross-country ride.