Top three (er more) reasons:

* Weather - it's ok to good all year round with the season (may-september) being always exceptional. You can climb as much as you want

* Rocklands + Cape Town has the best rock I've seen and I've been to tons of places (mostly bouldering though)

* The sheer amount - it's tons and tons of rock. The only thing that comes close is Utah, even boulder does not have that much rock.

* A little bit of non-climbing activities - safaris penguins, etc. Cape Town is a good tourist destination

* Food is excellent

* Surfing