Imagine your in charge of, say, taking care of a large planter. You need to bring with you:
- Half a pickup truck of new plants
- A few bags of fresh soil
- A few shovels, buckets, a hose, and other similar tools
They key is really just that vehicles are necessary to transport large quantities of stuff, regardless of whether or not it's a delivery vehicle. I think you'll find that a number of trades include low income workers who are moving around large quantities of stuff.
(This is not intended to be taken as arguing for or against congestion charges or any other policy involving shuffling money around, just against the logic of the above post and outright banning things other than delivery vehicles)