This article is full of inconsistencies. It's a terrible article.
For one the author says tennis expanded beyond the country club while golf did not - golf remained an "asperational" sport.
and
"The irony is that golf has thrived and tennis withered precisely because tennis has worked so hard to expand into a wider demographic. In the '70s and '80s, more public courts were built, more outreach programs were started, and racquets got cheaper and easier to use.
Golf has shed its clubby trappings much more slowly. ... For better or worse, golf has remained an aspirational sport in the American consciousness, an emblem of the road to success and prosperity. Golf's tent got bigger—and more meritocratic (even Tony Soprano plays golf) [why this makes golf more "meritocratic," I can't figure out] —but never lost its peaked shape [I don't know what "never lost its peaked shape" means].
Tennis, by becoming a mere sport, plunged into an identity crisis, and was left out of the bounties of American aspiration. [are baseball, football, and basketball "mere" sports as well? They are tremendously popular in the US. Do they have an identity crisis?] ['left out of the bounties of American aspiration," what the h*ll does that mean?]
Then the author says:
"The final insult is how, despite tennis's efforts to woo the people, the sport has never shaken its vestigial associations to the old WASP aristocracy. "
So first tennis spread out of the country club and onto the public courts, and then it never shook its connection to the old WASP aristocracy. Can't have it both ways here.
And the author says that golf got both bigger and more "meritocratic." But doesn't meritocratic mean limited on the basis of those who are deemed to be part of the meritocracy, thereby limiting its appeal rather than broadening it?
And does the author imply that golf didn't spread on to the public courses and that it remained in the country club. Maybe a little less so than tennis, but only a little. Golf courses not at country clubs and open to the public abound today.
And the author is on the wrong track if he blames equipment changes on tennis' supposed troubles (I think tennis' troubles are exaggerated, especially from a world wide perspective, rather than a parochial US perspective). Golf has undegone just as radical equipment changes. And like in tennis the changes have made it easier to play each sport rather than harder.
To the degree that tennis is less popular than golf in the US, I think it is because you must play tennis at higher skill level to enjoy it than is necessary in golf (it can be fun to ride around a green landscaped golf course even if you are spraying and losing golf balls all over the place).
But make no mistake about it, to play either game well takes a very high degree of skill - skills that to master might be, just might be, a little more difficult to master in tennis than in golf, since in tennis you have an opponent out to beat you (in golf the course is the primary opponent and in any case you can have a handicap to make things more even), and you have a moving ball to hit. But make no mistake about it, golf is a difficult game to master as well.
I think the real reason why more people are apt to "play" golf than tennis is that tennis is more strenuous, and most people don't keep themselves in good enough shape to play it, while golf, especially using golf carts, takes a modicum of effort. And the population is aging. It is even harder to play tennis rather than golf as you age, especially if you haven't kept at it and have becom sedentary.