Except most people in America don't park at meters. Not at work, anyway. Most people park in parking lots, where there's no infrastructure for charging stations. How many businesses would want to distract themselves with maintaining and running a network of metered charging stations?
I sometimes park in the Yerba Buena garage, which has eight floors and 2,585 spaces. At 5.2 kW each, it should be quite an engineering challenge to add thirteen megawatts of daytime capacity in the fully-built heart of San Francisco (for scale, that's over 1% of the entire city's peak demand concentrated into one block). If power were cheaper, maybe they could smelt aluminum at night to offset the construction costs.
Very few commuters into San Francisco would require charging while in the city, as the majority are commuting in from near distances. For those who do require power to continue their journey, it could be provided at a cost far higher than home charging.
It's rather silly to take the total number of parking spaces and multiply it by total possible charge to get your estimate of demand.
