People have been living in ships on the high seas continually for centuries. If your logic is true, then where are the Captain Nemo societies who don't consider land mandatory? Bear in mind that one of the well-understood issues about living off-world is the need for frequent resupplies from Earth.
To expand on your point, if one was to sustainably grow all vegetables required for a healthy, sustainable diet, then currently this can be achieved on around 100-200m2 per person (on earth, requiring no extra fertilisers / soil etc) based on research by John Jeavons. This hasn't taken into account external rainfall or air movement, but the basic premise is fairly well established. Throw in water treatment / recycling and humanure composting to close the circle completely, then all you need is a light source (assuming a closed atmospheric situation....)
Assuming that we can compress that down into 50m2 per person, the spatial requirements for a sustainable colony blow out quickly to large proportions, and we don't have information over the long term of just how well such a closed environment can nourish a small population - there's literature and research suggesting that we must have animal products in our diet for long term health, so that quickly adds up.
Given all these factors, supply runs from a known good source (earth / the mother country / home) are a sensible choice - but once you start roaming much further, it isn't an option any more. This is the stage we'll find ourselves at in 10-20 years time, as space travel will be economical to the point of sending out pioneer crews to space.
The closest long-term information we have comes from Biosphere 2. They spent a lot of time managing their ecosystem, and I think that would be true of any similar attempt for the next few decades. They had about 1500m2 per person, which included "water treatment / recycling and humanure." By comparison, ISS is 837 cubic meters, so assuming 2m for z gives a bit over 400m2 total.
We have a long way to go before getting that sort of volume. (Which, yes, is precisely what you said. I just wanted to work out the details for myself, out loud. :)
BTW, there's many people who have gone their lives without animal products in their diet, so I don't know what literature and research you are talking about.
I strongly doubt it will be economically viable to think of building (near) self-sufficient colonies for many decades. Brin's essay was very influential on me; it's much easier to build a self-sufficient colony in the Gobi desert (or the Sahara) than in space, so I would expect to see those first, if there's an economic need for the space.
If asteroid mining, or He3 mining of the moon, gives the economic impetus for a long-term off-earth location, then I look to oil platforms or McMurdo base as more relevant example.
