NIMBYism accounts for a lot because people hate change and people moved somewhere for a specific aesthetic but simple market demand accomplishes a lot.
I live in a medium sized Midwestern city with a burgeoning job market and plenty of restaurants/breweries/nightlife. I have a two bedroom apartment for less than $700/mo and it takes me less than 10 minutes to get downtown at 5pm. Meals for two cost $30 at a local restaurant with local beer. What I make isn't a lot, but it's a good deal over $38,000. That has to exist somewhere else too. I love my city, but I'm looking for new people and cultures (and I'm tired of -25F winters).
Anyway, take a look at Chicago.
Worth noting that this is quickly going away. Traffic is projected to get far, far worse over the next few years at current growth rates and public transit is still very disappointing in comparison to other large cities.
That said I love this city.