These flags are associated to your address when you choose your country at signup. Your address information is critically important for online transactions. On multinational e-commerce sites like WGT country (or region) is a required field. WGT does not get to choose how the countries or regions are represented. Those are dictated by the company WGT uses to process their payment transactions. Not VISA or MC themselves, but a payment processor like XiPay.
The only "choice" WGT really had in the matter was whether or not to incorporate that same flaglist into their design decisions. They did that and here we are today.
Messing with billing and payment code is generally frowned upon, so we can't use the current list of "checkout" countries. Honoring this request would require a second list of every country in world on which to base flag selection. This new list would need to be called instead and code updated to do so in every single place you see a flag appear. Forums, player lists, scorecards, profiles, game lobbies; literally every single place there's a flag on the website and within the gameclient. That touches a LARGE amount of files including almost every major function of the game.
From a software development perspective changing that many files at once is absolutely terrifying.
Unfortunately this is not an easy fix or a simple task. It's not just a matter of copy and paste or search and replace because WGT is comprised of hundreds of thousands of lines of code using a variety of languages across their various platforms. Some languages are sensitive to spacing, some are not. Was everything replaced properly? It would take some time, be a little tedious and a lot could go wrong. It would also require a major testing effort just to make sure this little change doesn't bork something in the game 4 degrees of separation away. Nothing is easy or simple when your source code exceeds a few hundred thousand lines.
There's also risk associated with having to maintain two distinct country lists. If a developer calls the wrong list by accident during a checkout request it could lead to some serious financial repercussions. Payments start getting rejected by the hundreds/thousands because "Scotland" or "Wales" comes over instead of the expected "United Kingdom". Now folks are irate because WGT is rejecting credit cards and won't take your money.
Then there's the WGT side of the decision. As WGT CEO, I'm not willing to take a chance on losing a large amount of daily income because some fresh-out-of-college noob or contractor in development accidentally switched the lists on both his/her second and last day. You'd think that kind of stuff wouldn't happen. It does. Technical experience does not necessarily equate to common sense. Not everyone is a winner.
WGT isn't going to do anything without a very strong reason to do so, and risk/reward is generally the deciding factor for things. There is no financial gain for them here and it isn't something they can use to sell to new people. "WGT: The only golf game with Scotland Flags" just doesn't carry the same weight as "WGT: Now with moar Pebble Beach!"
While the intent of this request is fully understood and appreciated it still must be acknowledged as a cosmetic one. One that currently carries a contingent of 8 unique people if I correctly counted the UK respondants on this thread over the last almost 2 years. While your arguments are completely sensible it's just not enough to convince me, as the decision maker, that taking on the aforementioned risks to offer this feature to so few people is a smart decision for the company.
Consider how many times this idea has been suggested, acknowledged
by mods, then gone silent. It
suggests that the requests are being quickly denied or put off for later discussion. There really isn't a "good" way to explain it either. Even the facts come off as pandering with an element of buck-passing, and trashing your vendors to your customers is not a good way to forge a good relationship with either. So, silence is often the best medicine. Better to leave a smoldering fire alone then to throw a liquid on it, which the fire may or may not perceive as gasoline.
While it would be great for all interested parties that WGT finds a way to satisfy your longing to truly represent your home nations there is a technical reality to the situation, so I would at least temper those hopes for now. Never say never though, right?
Anyway, I hope this provides some perspective.
Merry Christmas and all that fun stuff.
TL;DR - Technical issues(yawn), international standards beyond WGT's purview and potential risk factors(yawn) are more or less preventing this. All stuff that is true that we, as customers, don't want to hear.