If you're specifically talking about riding freight trains and camping under bridges (like Kevin Russ and Molly Steele in the article do sometimes) then I can understand. However, there is far more variety in these lifestyles than you or I even know.

Here are a few examples of one's I've personally met:

Family of 5 and a cat living full-time in an Airstream since '08. It's not novelty, it's sustainable and truly enjoyable for them.

Guy and his dog drive out of the city Friday nights as far as they can muster. Wake up with the sunrise, hike all day, camp overnight, wake up with the sunrise, hike all day, back home in time for work Monday morning. There's an incredible amount of drive keeping him active most weekends – passion for the outdoors – and he's going full-time as soon as possible.

77 year old retiree has been living on the road in various motorhomes for the last 7 years — an evolution of his years backpacking and traveling between work. Loves the freedom, loves the open space, is going to keep going as long as his health allows.