Within a parking garage is there a method of metering/constraining individual charging nodes so that the overall consumption does not exceed the amps available to the garage?
Say for example, all my neighborhood household electric meters have some zigbee coms that allow the electric co to snoop on individual usage closer to realtime. Do EVs not have a method for the charger to understand the EV's % of full charge?
But when we start talking about "every parking spot" scale, then two constraints come to mind: (1) the charging rate is too low to be effective (L1 charging over "regular" 110V wall outlets gets you only a few miles of charge an hour), and (2) if you have too much current going through some common section of cable, it will blow a circuit breaker, or worse, overheat and cause an electrical fire (same as if you plug too many things into an extension cord at home or work).
Edit: I think the current state of the art for sharing is "push notification to tell the driver to move their car" because there is a non-trivial capital outlay for chargers even if you have enough electricity. So any scheme that involves all the cars being plugged in and some intelligent switching of who should go first still requires considerable capital costs, even before you get to upgrading the big transmission wires.
in the case of a general purpose parking garage, this is less okay. I don't want to park in a garage for an hour to shop and not know whether my car will be at 30% or 80% charge when I get back. this is barely better than not having charging infrastructure at all.
We'd need some pretty serious upgrades to our electrical transmission infrastructure to get L2 charging speeds from "every lamppost" as some would propose.