How come this isn't more common?

Boulder, Colorado, has become the latest location to offer public free wifi with the access points powered by the sun. The solar panels can charge the system battery in about 5 hours, and the battery can operate the access point for up to 72 hours. The network can therefore remain up day and night, and the manufacturer, Lumin, claims that the panels are sensitive enough to "register a charge from the moon" -- unstated is just how much charge, but no matter: under nearly any conceivable scenario, solar powered WiFi access points could remain up and running without interruption for very long periods of time.

Although Lumin and other solar panel access point manufacturers talk about the usefulness of their systems in the wilderness or in war zones, I can't help but wonder why these configurations aren't in greater use in more urban environments. By definition, a WiFi hotspot doesn't need to have cables connecting to client computers, and if you hook up something like an EV-DO card, it doesn't even need to have a cable connecting to the Internet provider. Why should it have a cable connecting it to its power source, then?

(Original link via Roland Piquepaille)