One also has to consider that new families with young children are high on the list of demographics looking for suburban homes, and are likely to have less money, so suburban homes are cheaper by necessity.
Cul-de-sacs wouldn't be so bad if they had well-maintained pedestrian lanes that cut between them and neighborhood shops instead of big box stores.
In England at least, a poor area still has little cafés [1]. The menu is similar enough — fried breakfast etc — but it will be served on an actual plate, rather than a chopping board or slate. The choice of restaurant might be a larger pub, or a place that also/only offers take-away (McDonalds or a small Cantonese place, for example). The market probably has less promotion of organic produce, and will sell produce as well as cheap clothes and household goods.
I used to live in a poor area of London, which I think was built in the 1960s. There were cul-de-sac roads, but most of them continued with footpaths so journeys wouldn't take too long. On the main road there was a school, church, doctor's office, dentist, library, small grocery store, beer/wine shop, bakery, cheap café, pizza take-away, Chinese take-away, Indian take-away, fish and chip shop, pharmacy, newsagent, youth club and 'village' green including play equipment. The pub-with-dining had recently closed, I'm not sure if that's still the case. All of this is within 5-10 minutes walk of most people, beyond that distance and they are close to the next cluster of shops.
There wasn't a market, but there was a market selling fruit and veg in the nearest 'town', which was about 5-10 minutes by bicycle, or 10-20 by walk+bus.
[1] http://www.constructionphotography.com/Details.aspx?ID=11957... — "builder's caf" or just "caf" is a slang term for them.
Most places, the closest thing you're going to find to a little cafe is your local 7-11 or Dunkin Donuts. Or the local package store. Generally, people go to the supermarket once a week, and they stock up enough that they don't have to go to the market every single day - when I spent a few months in Germany, this was one of the differences that struck me most oddly. Art is generally... not held in great esteem.
All of these things end up being plentiful, cost-sensitive, and profitable when the space you live in supports and encourages plentiful foot traffic.
But sure, the real test would be non-walkable neighbourhoods next to city centres.
I suspect this has more to do with fact that walkable areas are much more likely to be located in city centers with higher overall real estate prices than with the desirability of walkable neighborhoods.