Is it strictly the imposition of northern mentalities ?
The desire for "GREEN ?
Speaking for Arizona, I think it is definitely the desire for green driven primarily by the tourism economy.
The warm winter climate brings lots of tourist dollars and there is a glut of courses competing for those dollars. Course A overseeded with lush green rye grass will attract more business that Course B with dormant turf. That's a fact Jack.
99.9% of the golf public perceives green as the expected color of a golf course and the dormant surface is brown and brown is equated with dead, undermaintained grass.
When I first moved to the area 35 years ago, there were only a handful of courses that would overseed more than greens and tees. By the end of the 90's, virtually every course overseeded greens, tees and fairways with quite a few of the high end courses including the roughs in what we call a "wall to wall" overseed.
Only in the past few years have I noticed an increasing number (still relatively few in the overall picture) of facilities cutting back and letting the fairways go dormant. A smaller few even forgoing the green overseed (more popular with the newer ultra dwarf strains of Bermuda that seem to have a shorter dormant period). I'm sure it's a trend that is economically driven as I understand it is quite expensive to overseed. Unfortunately, there are few golfers that recognize the joy and playability of the dormant surface and these facilities will struggle to compete.
I always say the the overseed screws up the course twice. A full two months (or more) of misery during the fall grow-in, the success of which is a crap-shoot based on unknown weather (see Steve's mention of the failure at Dove Valley Ranch). A course can't just close and start the overseed when the weather report looks good. They have to set a date on the calendar months in advance and hope for the best.
Then in the spring, when the Bermuda should start growing again in March, it has to compete with the rye up until May or June, and when the rye finally dies off, you've got stressed Bermuda trying to come in during the hottest and driest period of the year. So you get another month of patchy conditions which improve through the summer, aided by the July/August "monsoon" moisture and humidity up through mid September when the summer turf is in absolutely the most brilliant condition - just in time to be scalped down and the whole cycle starts over again.