The density in cul-de-sac neighborhoods is still too low to make it possible for residents to get to any of the basic services they need (school, grocery, etc) without driving. Adding a few roads to shave a mile or two off a commute or trip the store isn't going to make much of a difference. Our (american) cities desperately need urban growth boundaries to force density.
Why are you/we trying to force density when it's so obvious that most people want the exact opposite? [edit] I had in a house in a great neighborhood in the city within walking distance of grocery, restaurants, buses, etc., and I still moved to the suburbs. Obviously density's not the only thing people want.
I live in downtown Portland, OR and have done so for the last eight years without ever owning a car. I can walk or bike to literally everything in the city, or alternatively take a streetcar, light rail train, or technologically advanced bus system. There's a reason people move here – there's value in Urban Growth Boundaries (UGBs) that make more livable, walkable, awesome places to live your life.
And because of the UGB, it's even faster to escape the city's limits and find yourself in real green space. On Tuesday after work, I drove 45 minutes (using a car-sharing program) out of the city to a national wilderness where I slept under the stars, caught a few trout, and still made it back into the city for work the next morning. Something like that might be difficult in LA or in a large suburb.
As you can see, I really really disagree with you. :)