All this "no cruise control on hills" is garbage, at least for some rigs. On my current Newmar Ventana and on my previous Beaver, I use(d) cruise control quite a bit, including through the Rockies. However it DOES need to be shut off on certain occasions, less so on my Ventana than on the Beaver on the uphill, and less on the Beaver than on the Ventana for downhill. And there are times going uphill where I'll manually shift gears earlier than automatic would do it.
The differences are due to the way the cruise control behaves on the uphill and the differences in engine brake for the downhill. On the Beaver, once the speed (with CC on) had dropped some large amount below what was set, the CC would disengage automatically, whereas I have yet to see that on the Ventana, thus can just mash the pedal down (something that was discouraged on the CAT-driven Beaver) to keep speed up a little.
On the downhill, the Beaver had a two stage engine compression brake, and even down from the Eisenhower tunnel to Silverthorne (6% plus) the 2nd stage didn't let the speed get much above 60 mph, while the Ventana has a VGT, Variable Geometry Turbo, in the exhaust, which is much less effective and needs careful attention to not get too fast on all but the shallowest of hills.
One other big difference in the two rigs was that on the Beaver you could not use the compression brake with the cruise control on- engaging it shut the CC off. On the Ventana I can leave the VGT on all the time, even with the CC engaged.
SO a lot of the discussion above seems to be either based on how someone's specific rig behaves or some preconceived notion of what a "driver" is.
So as with so very many other things, it all depends...