Heh, funnily enough, a few years ago I was at a rodeo with some friends, and this was in rural Oregon. One of the announcers was a radio personality on some country station in the Portland area (I think -- something like that, at least).
For most of the rodeo he spoke with a thick drawl, obviously going for the "good ol' boy" vibe.
A few times, he slipped up and spoke with a very plain Portland/PNW accent. It was jarring when I heard it but he went right back to the good ol' boy accent and I don't know how much anyone else noticed. But it came across like it was all an affectation, for the reasons you described.
Honestly, I do this a lot when I'm back visiting relatives who live in the southern US; my neutral accent goes out the window and I add a little twang, speak more slowly, and say things like "thank you ma'am" a lot. It's kinda second nature since I went to school in a rural-ish area (University of Florida) and it makes a shockingly big difference in how people treat you sometimes.
For most of the rodeo he spoke with a thick drawl, obviously going for the "good ol' boy" vibe.
A few times, he slipped up and spoke with a very plain Portland/PNW accent. It was jarring when I heard it but he went right back to the good ol' boy accent and I don't know how much anyone else noticed. But it came across like it was all an affectation, for the reasons you described.