Companies interested in deploying Wi-Fi networks covet the bands of spectrum on which broadcast television currently resides because of its inherent scientific properties. Signals at that frequency travel straighter and farther. Consumer advocates say using the spectrum would enable cheaper and easier set-up--and thus more widespread access for rural and low-income areas.
Less than a decade separates us from the time when the Internet was a nerds-only playground, and the demand for readily available, cheap access is only growing, so it makes sense to use whatever resources you have available to make it happen. Eventually, all that space will be available anyways, at least in the U.S., with analog television going the way of the dodo in 3 years. A much larger amount of people can receive analog TV signals than can receive Internet access, and thus the ISPs and manufacturers have seen a perfect niche for future growth. Those antennas may still have some life left in them.