England is a very different country from any of the other component parts of the British Isles, with over 56 million inhabitants, against less than eight million on the island of Ireland (ie both sides of the border), five million in Scotland and three million in Wales. And that has a number of different consequences.
Firstly there can't sensibly be any countrywide marketing campaign on the lines of the iconic "Wales: Golf as it Should Be" campaign that really created the golf tourism industry in Wales. There are regional groupings in some areas such as the "England's Golf Coast" organisation that markets the Lancashire links, but a nationwide one does not and cannot exist. It's impossible to brand 'English golf' in the same way -- it is too big and too varied. The distances involved are too big as well -- if you were stupid enough to arrange a trip on which you played Goswick after St Enodoc, you would be signing up for a 500 mile, ten hour drive -- the longest comparable distance between two high end courses I can come up with in the other countries is a 290 mile drive between Southerness and Dornoch. And so "going to play golf in England" will never have the same identity as going to play in one of the other countries.
Then there is the fact that, in general (though there are obviously areas where this is not so) England is significantly more affluent than the other countries. So many of the top courses do very well thank you just from their membership fees and the visitor income they get without doing a lot of marketing. I know that Sunningdale, for example, does a massive sum (the last number I heard was about £2 million a year) in total visitor revenue, and that was before they put the cost of a 36 hole day plus lunch up to £500! Clearly there are fine courses in England that would very much like more visitor revenue, but it isn't really feasible for an individual golf club -- especially one in an area that isn't on the beaten track and is not desperately well-off -- to market itself to overseas visitors, unless, like say Royal Dornoch, it already has iconic status. For any golf club, a balance has to be found between serving its members and attracting external revenue -- Dornoch is the key example here, it must earn the highest proportion of revenue from non-member play of any golf club in the world; it is no wonder that it feels like a very high end pay and play sometimes. Clubs in more affluent areas, with a substantial number of members who are themselves reasonably well-off and successful in life, don't want to go down that route.