Although I have also experienced this several times in the upper Midwest. I suspect there might be some bias in my physical appearance that makes me get offered more? Several drivers had a sort of setup where they had goods in a box/console and opened it to make the offer, so it seems likely that if they didn't feel a fare to be the partying type they would simply not make the offer? One I saw had an entire cooler setup.
Another possible explanation could be that in very competitive areas like LA or the Bay the rank/yank system cuts out bad drivers more quickly than middle-america where there is maybe not as large of a pool of people applying to be drivers?
I have never had a bad or sketchy ride in Bay/NYC/Chicago/Dallas. (I have had no experience with Uber in LA)