I can't disagree with any of your observations.
Dealers buy & display makes/models they think they can sell and most focus on the mainstream buyers, which often means newbies. And dealers generally know (or at least believe) that low prices and high bling are what attracts buyers the most. Winnie isn't noted for either of those, solidly middle-of-the-road. They are perhaps also stronger in middle America rather than either coast, simply because of proximity to the factories. Physical delivery of RVs is a major factor for dealers, both for time and cost. The lower price of most trailers vs motorhomes makes the delivery cost a bigger factor.
To many Americans, Winnebago is synonymous with motorhome, but not trailers. The brand name is recognizable but just doesn't have the same impact.