Even sexier (and less field-tested) than vertical turbines are windbelts.

https://en.wikipedia.org/wiki/Windbelt

> Prototypes of the device are claimed to be 10 - 30 times more efficient than small wind turbines. One prototype has powered two LEDs, a radio, and a clock (separately) using wind generated from a household fan. The cost of the materials was well under US$10. $2–$5 for 40 mW is a cost of $50–$125 per watt.

I think the reason plainly is that they are not competitive, perhaps because their advantages aren't important enough disadvantages for horizontal axis turbines.

Wikipedia has a short section:

https://en.wikipedia.org/wiki/Vertical_axis_wind_turbine#Dis...

I think people tend to forget that the big wind turbine manufacturers today started out small, experimenting with various designs before they settled on the three-bladed model. At the moment there's a lot of accumulated research and infrastructure present that allows them to erect giant 3-6-8 MW turbines that can take the hammering of the weather for > 20 years. Competing against this is really, really hard, you really have to a big advantage in your favor and perhaps also decades of research and development.

Scaling issues, I think - they need to be supported at the top as well, and they're dependent on how much weight and wind force the bearings can take.

http://www.windpowerengineering.com/design/vertical-axis-win...