Mine came with one, but, I suspect, in a cost saving mood, the manufacturers have determined that they really aren't necessary. There is very little on the roof that is serviceable by the layman and the coaches are so tall that storage up there (not to mention roof loading) is non-existent. The ladders themselves, being straight up and down are not easily climbed and put a great deal of horizontal pull stress on the mounting points. Where I have my coach serviced, they take the lower part of the ladder off and then use an "A" framed step ladder (left folded) leaned up against the remaining stub of the coach's ladder to gain access. Much easier to climb particularly if you are trying to carry something up there to either affect a repair or install a new "gizmo" (vent cover, antenna, etc.). That is basically what I do...I have one of those 7' folding ladders (folds to 3 1/2 square designed to fit in the 4" bumper) from my trailer pulling days. I lean that against the existing ladder, climb it and then I'm close enough to the roof, I can set my toolbox and whatever I'm working on up onto the roof. I then climb the last little bit of the coach's ladder to the roof.
If I didn't have the ladder already, I'd just get a collapsible ladder and carry it in the basement or the back of the towed. I have one from my trailer days (never had a trailer with a ladder) and it was handy for one thing...if you don't have slide toppers, the extendable ladder made getting the slides cleaned off much easier before pulling them in. In fact, for most folks, that would be the only reason I could see now-a-days for having a ladder on the back, but, I'd still rather use a ladder that leaned against the coach as opposed to straight up; much easier to climb while carrying a broom or anything else, for that matter.
But, to answer your original question...owning a DP doesn't mean you can't have a ladder. If you want one, contact the manufacturer of your coach to ascertain whether one can be added to your Itasca; it may not be possible if there aren't adequate areas that "blocking" can be added. Blocking goes on the inside of the fiberglass rear cap to support the ladder's vertical and horizontal stress so that the mounting hardware doesn't pull out. Any "good to great" service department at an RV dealership would also be able to help you out on the advisability and work necessary to add one to your coach.
My 2 cents, your mileage may vary...
Don
Bronwyn
Down to 1 kitty...J-Lo, the princess
2014 Thor Tuscany 40RX
2015 Jeep Cherokee TrailHawk Towed
