Water and food are indeed trickier; the Moon does have some trace amounts of carbon (deposited by solar wind) and hydrogen (at the poles), but extracting enough of those elements to sustainably support living there is unlikely unless we make some major discoveries or figure out a more reasonable way to import such things (one idea is to capture hydrocarbon-rich asteroids and park them in lunar orbit, but that ain't exactly my idea of "reasonable").
As for profitability, the Moon happens to be rich in silicon; a far-fetched idea might be to build a whole bunch of lunar microchip factories. The Moon is also full of raw materials in general, and getting them into space (e.g. to build spacecraft or to import to Earth) is a lot easier than getting such material into space from Earth. This makes the Moon a potentially-valuable staging point for missions to Mars and elsewhere.
If there is indeed water (or some other hydrogen source) on the Moon in sufficiently-abundant quantities, lunar fuel depots would actually be feasible; there's been quite a bit of work in recent decades around using silanes (hydrosilicons) as a useful fuel, replacing the need for hydrocarbon-based fuels (or using hydrogen directly).
http://arstechnica.com/science/2016/11/high-temperature-rock...
You're correct in that large, (comparatively) easily mined water ice deposits are located in permanent shadow at the poles, but there is likely water available in most locations, if you dig down below the surface.
Also, why is a metaphor needed here?
A metaphor compares two things similar from a certain aspect -- they could still differ in every other way. One could use a metaphor from agriculture to clarify their point on a political issue, for example.
>Also, why is a metaphor needed here?
For the same reasons that it's needed elsewhere. To get the point across in a simplified way, because people can understand a phenomenon better in one domain than they can in another (aka "domain dependence").
When I said "the metaphor compares two similar thing" I didn't mean metaphors in general, I meant your metaphor specifically compares two things that are similar. The relevant differences between NY and the moon do not exist between NY and Illinois.
> For the same reasons that it's needed elsewhere
Metaphors are often of dubious value. They can be used to clarify unfamiliar situation, where the bounds of the metaphor are clear; or, perhaps as in this case, encourage similar thinking about two related concepts.
But you provided a metaphor here without providing clarity on what the point was. When I think "why would I build a city in Illinois, when there already one in NY", none of the answers I come up with apply equally to the moon. e.g. land is cheaper/convenient (not on the moon), the scenery is better (maybe true, but not to outweight other more pressing concerns) etc.
While that certainly would be awesome, I'm pretty sure you meant "solar system".
We actually have more than that; in addition to Curiosity, the Opportunity rover is (by some miracle) still in active service and fully operational.
I feel a lot of the return on spacefaring is as simple as making groups of humans, a long way from each other, work together because of shared interests.
Society has accomplished a ton due to the space race. Furthermore, just because we haven't put humans anywhere doesn't mean we haven't explored anywhere. We have a robot on Mars, had a robot on Venus. We have ships nearing the end of our solar system and sending data back. We have learned tons, and keep learning tons, and have used all of this knowledge to make life on earth better. GPS alone is worth it, let alone everything we've done.
Putting more men on the moon does us absolutely no good besides letting a country puff its chest out more.