Actually, most of the water we drink does come from relatively nearby (particularly relative to hauling ice from the poles). There's a reason the Sahara is not densely populated. Likewise for our food.
Most of Mars' water is at its south pole, which is so cold that much of the water ice is actually buried under a layer of "dry ice" — frozen carbon dioxide.
Basically, anywhere you are on Earth, you're closer to nutrition and fuel than you would be anywhere on Mars. And the reason why can have diets that don't involve foraging is because we've grown so numerous. That's also something that isn't true on Mars.
My point is that the norm for folks living in the developed world on Earth is for their food, water, and housing to be obtained via a very technologically advanced and typically world spanning industrial supply chain. The amount of effort and technology that goes into something as simple as buying a single hammer at the hardware store or turning on the faucet and getting fresh drinking water is stunning. The difference between what's required to support a Martian civilization and an Earth civilization is not so much a difference in fundamentals as it is merely a difference in degree. And possibly it's less of a difference between, say, living in New York city today and living on Mars in 2030 than NYC today vs. NYC in 1800.
As far as water, the largest deposits of H2O on Mars are near the poles but it exists in enormous quantities at nearly every location on Mars a few meters below the surface.
Most of Mars' water is at its south pole, which is so cold that much of the water ice is actually buried under a layer of "dry ice" — frozen carbon dioxide.
Basically, anywhere you are on Earth, you're closer to nutrition and fuel than you would be anywhere on Mars. And the reason why can have diets that don't involve foraging is because we've grown so numerous. That's also something that isn't true on Mars.