Many of us don't like living out of a backpack and won't do it for recreation. Truck camping is great, but
owning a truck is generally a stupid thing to do. (
)
A trailer is great for storage and once you're in place that storage space can easily become living space. Living in a tiny box sucks, so doing it up as a tent multiplies the amount of space you get out of it. You get storage, ease of setup/takedown and a yuge increase in civilized living.
I love having a pop up, but having one done right would be awesome. Freebeard's sketch looks a lot like what I saw a couple weeks ago: some guy tore the rear ramp off of one of those Home Depot landscaping trailers and built a nice teardrop on it- but what he was living in was a large tent set up behind it. It's a good compromise because I'd hate to scrounge pop up parts and try to build something workable, much less design and sew the tent part.