As for why.....to be honest, there is a certain segment of the population that just do things differently than the rest. Not better, just different and it's a very steadily growing community that is doing this. Eventually, one of the RV companies will get in on this and put out something similar for much much more $$$
I use to get asked a lot why I jumped out of perfectly good airplanes as a Paratrooper....the answer...."Because" ;)
I have a link I found a while back about a guy who also did this. I piggybacked onto his idea and he piggybacked onto someone else's.
Lots of photos.....
Franken-Camp