Problem we found with attaching them to the back (or front) of the Motorhome is, sometimes we like to be able to take the bikes places with the towed vehicle. Didn't want to be tied to only carrying the bikes with the Motorhome. That, and if you look carefully at the fine print, most hitch mounted bike racks are not even recommended/warrantied to be used on the back of an RV, due to all the bouncing that takes place back there. I seem to recall there is only one or two makes out there that support this use.
For a while, I did use a hitch mounted rack and attached it to the back of the towed vehicle (Ford Fusion at the time). That didn't work too good for us, either. Hated how trunk access was taken away. Last straw for it was one time we hit a large bump that snapped the bikes around so bad, the strap connecting the rack to the trunk lid jerked so hard it twisted the trunk lid and caused some pretty major damage (trunk lid had to be replaced). Fortunately, insurance covered the damage, but that was the end of my days using hitch mounted racks.
I ditched the hitch receiver bike rack for good, and went with a Yakima roof mounted system. Now, we carry our bikes on top of the towed vehicle. Can carry up to 4 bikes this way if I need to, and can be just about ANY kind of bicycle. Roof rack can be used to carry several other things, too, if the need arises (kayaks, storage bins to name a few).
Yes, this approach is more expensive, but you can minimize the cost by buying many of the parts on Craigs List or Ebay slightly used. I saved several hundred $$ going that route. And, when towed vehicle (Ford Fusion) was totaled in an accident a few years ago and we were forced to replace it, the roof rack fit perfectly on the new towed vehicle (Taurus) that replaced the Fusion.
Now, bikes don't touch (scrape against) each other or anything else, are held in place by the wheel only. Completely out of the way, and very easy to take down and put up. And no more (or at least nowhere near as much) bouncing around for the bikes. I highly, highly recommend you at least look into this approach. It works great for us.
Will and Cheryl
2021 Newmar Baystar 3014 on F53 (7.3 V8) Chassis ("Brook")
2018 Jeep Wrangler JK ("Wilbur")