It's a personal choice, usually dictated by the goals of the journey and the depth of the pockets. People ride bicycles around the world, and people sail across oceans in 14 foot open boats. But that's a level of discomfort that most of us couldn't tolerate. While a Jeep and sleeping bag works for a week, I doubt many of us would care for it after 2 months.
There's something to be said for keeping it simple. I met a guy in a campground in the Sierra Nevada. He said he bought a used 4x4 Ford Ranger with a bed cap, stopped by Wal-Mart to pick up some inexpensive family camping gear (tent, sleeping bag, camp table and chair, Coleman stove, and so on), and hit the road to conduct a personal safari across North America.
When I talked with him, he had been traveling for 6 months, following the changing seasons north. He spent his time interviewing people he met about what they value most in life. I think people's reactions to him would have been different if he pulled up in a million dollar ExPo vehicle.