I mean how many people move into retirement and then start playing rugby? The answer is not many, if any. We all know that to the average person, golf starts seeming like a pretty good fun when you are nearing 80. There are many notable examples of this - with the late John D Rockefeller pioneering this trend after he had finished with his standard oil developments.
So what one is saying is that golf does not require the level of athleticism that other sports do. I am not saying that it is not utterly exhausting to play a round of golf- but one could just about get away with chain smoking cigarettes and still make it round.
But it does require athleticism - indeed - when one is too old one cannot compete with the younger players. This is why they have set up the senior tour for the older players. It is no coincidence that Tiger Woods can hit the ball further than everyone and is the best in the world.
The other thing about golf is that one is really competeing against the elements and oneself. The person who may be ones closest rival in a tournament may be half a mile away all week. This does seem to suggest that golf is more of an individual pursuit than a sport.
Also I have heard people argue that there is no real danger in golf. This is not 100% true though for people are always getting injured, and of course the first thing that one learns on a golf course is the meaning of 'FORE'.
Either way it seems clear that golf is here to stay as people seem to be absolutely obsessed with it for better or worse. People who argue that competitive golf is not a sport dont really frequent the course.
I personally love a good round now and again but as Mark Twain one stated "golf is a good way to ruin a walk", it is clear that not everyone feels the same way.