Minimum, (and therefore average), car parking space in UK is 2.4 metres wide. Average car width in UK is around 2 metres.
This gives a space of 30cm either side of a car. Which equates to around 12" either side. How ludicrous is this in this day and age?
BTW, average width of the car does not include side mirrors, some of which don't fold in when you park.
Usage of space can be improved if everyone parked alternatively, nose to tail, passenger door tight to passenger door, so the bigger space is for the drivers to get in. Passengers can always jump in, once the car is extracted and more often than not, it's the careless passengers getting in and out who cause the door dings.
When I get in or out of the driving seat, I wrap my fingers around the outside of the door, so my fingers cushioned the door from dings again other vehicles.