I think you're missing a key ingredient which SF, Austin, Boston, etc have: established technical universities bringing and growing talent in from across the gl

I think you're missing a key ingredient which SF, Austin, Boston, etc have: established technical universities bringing and growing talent in from across the globe. University towns can be a hotbed of startup talent if they are combined with a wealthy populace that continually injects capital into young companies starting out of school projects and/or research. While companies that start out that way don't encompass all startup growth, they continuously seed it through up and down markets to make the local startup ecosystems more resilient through economic downturns. Without the universities, the best you can do is have market-fueled startup boom/bust cycles like the ones in Dallas, LA, NYC, and San Diego. NYC is trying to break out of this cycle with more economic investment in education and they may pull it off. That being said, I think asking yourself why there isn't a startup culture has a lot more to do with education/talent than it does with what technology du jour is currently popular a city.