Many high end coaches do not have it. A couple reasons. Cosmetically, they feel it detracts from the look of the coach. Practically, it's almost impossible to mount one properly on a coach that's over 12'6" or so. I think the RVIA requirement for a mounted ladder is that it must project 1' or so above the roofline so you actually have something to hold onto when you get to the top. On my coach, the end caps and top of the awning mounts are 13' or so. There's just no available vertical room to put a ladder over the top of the end cap.
2008 King Aire 4562, Spartan K3(GT) w/ Cummins ISX, Motosat HD-SL5 w/ SWM-8, Multiswitch, HR34 Genie
2014 Jeep Grand Cherokee Overland 5.7L V8 Hemi w/ Blue Ox Aventa LX Tow Bar and baseplate, SMI Air Force One brake