of course parents need extra width, just as disabled do, the extra width allows babies to be comfortably carried into a car seat, to safely move a disabled person into a car.
the doors on a car with children are likely to be open wide as opposed to a person on their own who can shimmy into their cars.
People with children and disabled tend to carry more equipment with them.
why ban them when they serve such a useful service, maybe the able bodied or people without kids need to learn to walk a bit further without moaning