UPS trucks do shut down at delivery stops. I've never seen one that didn't. I think the latest trucks are hybrids.

Big rig drivers don't shut down because those big engines are hard to start from cold. NYC now limits idling to three minutes, you can actually get a ticket if you go longer.

Starting is damaging from a cold start, because the lubricants have leaked down and viscosity is high. If the engine is hot, not so bad. Hybrids turn on and off all the time.

The only time I let the engine idle is if I have to stop immediately after getting off a fast road. Letting the turbo temperature drop a bit prevents oil from boiling out of the bearings when it's stopped. a minute of cool down is a good idea.