I don't know about you, but I don't go camping on the side of the road. Most places I go tend to not have roads. At most a named track.
Maybe Im not explaining it clear enough. You need to think further than yourself.
These companies are making trailers for 1000's of other people.
What 1000's of other people want is what they design their trailers for.
... Most people dont camp on the road, most people camp off the road. but most people stop on the side of the road for lunch, or a coffee, or sanga, or drinks for kids and stuff.
Its not just the camping that is the issue, it is while travelling.
Maybe look at the section here and build your own.. dozens and dozens of people doing it as they cannot find exactly what they are looking for either.
http://podtrailer.com.au/products_pod.html try the pod as mentioned.
I'll leave it there