I think the central premise of this thread (or what I surmise it to be...) is a pretty good one, and Kalen touches on it in his responses (and gives a good example in Indian Canyon, by all reports a really interesting course that architecturally could be considerably improved with some modest and thoughtful expenses).
My experience in Wisconsin might be relevant here, in that the complete opposite of what Ben suggests has happened. Twenty-five years ago, Wisconsin had virtually nothing in the way of high-end offerings. Now it's a virtual mecca of well-regarded (by most...) golf destinations: the four courses of Kohler, Erin Hills, a Jack Nicklaus signature course, a renovated and much-improved SentryWorld, and two (perhaps more) Sand Valley courses by Mr. Bandon.
Does visitor traffic account for a lot of this? Sure, probably...but one can't help but think that golfers in this state have grown to acknowledge and admire better golf architecture, and support it. Regardless of one's particular view about the merits of, say, Whistling Straits, there's little doubt that golfers here have much better access to quality architecture than a generation ago.
But it's costly golf, and one that I also suspect has sapped growth from some of the 3s of the world (or, the state). And that's been my experience -- most courses here have simply adopted a go-along-to-get-along philosophy, it seems, and are content to keep offering what they do, with little effort to improve their courses. Meanwhile, deep-pocketed folks are buying up land to fulfill their personal fantasies (Ballybunion by the lake, Pine Valley a short drive from Chicago), and have it supported by charging deep 3-figure fees for a round of golf.
Isn't there some kind of middle ground here -- a 3 that with some appropriate, fairly modest, but thoughtful renovations, could be turned into a 5? If if it's good for the game to add the Sand Valleys of the world (which draws near-unanimous hosannas around here), isn't there also room for some 3s to become 5s without the kind of deep pocket investments that tend to dominate the latest architectural discussions?