I think that's a point well-made (at this thread). ........In fact, as a general rule, I can't think of much point in improving ANY tile outside one's city borders......Unless, like me, you've played a multi-month HOF Histographic game and just do it for aesthetic reasons as a celebration of being done with a long game!
Happy New Year everyone.
1. You'll have it later, and you don't have enough for your workers to do inside your territory
2. You want to hook up a luxury or resource for the AI so you can trade for an extra source.
3. So that the effects of global warming strip a forest outside of your territory, instead of causing a plain to become a desert or something silly like that.