I think this is a little strange of a question, but then again I'm a very hardcore golfer.
I would liken this question to asking a baseball fanatic why would it be appealing to do batting practice at Fenway or Yankee Stadium? Aside from these being among the best courses in the world, golf fanatics have watched PGA tour players struggle on these courses for years. And now they have the opportunity to see, appreciate, and maybe even attempt some of what the PGA tour players have done.
I've played a few major courses in Scotland - Carnoustie, Turnberry, & Prestwick. At the time I played these courses (94) I was about a 3 handicap - I shot over 90 at Carnoustie. It was a hellish round and extremely difficult, but it was awesome at the same time. I can recall just about every hole and every shot I had there and this was 14 years ago. I can't recall many other rounds I've played, but over there I remember just about every course - because of the history and it was special.
I think most non-golfers or casual golfers don't appreciate just how good the tour professionals really are. Playing these types of courses, when a person is fortunate enough to get the chance, will give them quite a perspective on the sport.