First off, I've never played WoW or any other pay-to-play subscription game so maybe there is a good reason. Second, I don't need gil in the game, it's just a game and scratching for resources is part of the fun. I'm in no hurry.
But, what is wrong with allowing players to buy gil in the mog station?
I don't see how it can hurt the game economy. It would put more gil in the auction houses. I can see how someone would be concerned that cash players might have an advantage but as far as I can tell there is no losing in this game.
If you die, you don't lose exp or items or anything so..heck I don't mind dying, respawning and getting back into battle - death is meaningless. Similar with racing to level 50 - if you are in a hurry so what? Everyone who wants to will get there eventually. Slow or fast, progress is guaranteed.
Anyone who knows more about these online gaming economies have a good reason?