Here in Texas, it is assumed a motorhome has a generator. It would be similar to assuming the motorhome has a steering window and accelerator pedal. Without it, people will look at it and pass it by. I definitely would not buy a motorhome without it, because A/C is so important, and even when on the road, I'd be running the generator to keep the roof unit running.
Michigan may be different, but unless one has a good solar charging system, the generator will still be needed to keep the house batteries charged up, and for electric heat, if one doesn't want to use their propane.
I'd say get it. You may not use it often, but when you need it, you will be happy you have it.