If you use the toyhauler to haul off-road style toys or a small fishing boat into the unimproved campgrounds where power isn't available then having a generator is a asset. If you do not have a stout solar system then I think it moves up to a requirement.
We use our toyhauler as described above, just as we have used every other RV we've owned over the past 3 decades.The generator has driven everything from a small 120vac wire-feed welder, to the AC to a small TV with a VHS player in it. (kids thought they were in high cotton).
We have a 4k Onan onboard and also take a EU2000 Honda with us. The Honda will handle most needs and serve as a back up and the Onan will take care of the rest.
In the evening, if we are just running a battery charge to get topped off for the furnace to run all night we will run the quiet little Honda on eco-throttle and it is very quiet.
If you are not using your toy hauler like we do,you could do without the built in generator. Different strokes for different folks, but in my circle of friends I cannot imagine any of us not having a generator on board. As time passes I do plan to do a substantial solar system for a number of reasons, but I still won't be without a generator. Redundancy is a wonderful thing.