What's wrong with a roof rack? Why do you want your ladders inside your van?
roof racks are fine - but how neat and tidy is a ladder that stores in your van.
more secure
quicker and easier to get in and out (instead of on and off)
i only use the ladder for access as i'm water fed pole - so nice to have ladderless
on sign writting and no ladder in sight.
no concern about is it going to come off when i'm doing 98 down the a12.
also a smoother ride with better mpg.
lastly i just like the look of a van without ladders on top