Joe,
I enjoyed your blog on the subject. A few thoughts,
While I don't know who designed logos of yesteryear, I believe most current ones are designed by the shirt companies gratis or low cost with the primary aim of selling their shirts. So, the basic motives have gone commerical, but that is also true of the public courses who have to sell their shirts to one customer at a time, and much like their courses, look for a "signature" logo that stands out visually at first glance. And any logo must stand out on a variety of shirt colors now, whereas I presume white and gray were the most likely golf shirts of an earlier era. (maybe tan and olive?)
Maybe its just a sign of the times. I will note that many courses try a few different logos out now, and settle on the final based on the first year of sales. Some still keep some variations, which kind of dilutes the brand a bit.
Not sure exactly what old private club logos were intended to do, other than perhaps signify snobbery. Different eras do seem to have a certain trends to them, with Sand Hills updating the old simple look, trying to convey a feel of the old time classic to match the course (I presume)
You can almost tell the era by the logo, much like the muted Apple logo. Almost like the 60's era NHL expansion teams (Flyers Orange) vs either the original six or modern teams, like teal clad Sharks.