I was at an outdoor wedding recently and I could hear a truck idling behind the hedges so I went to investigate. It was an AAA tow truck and the driver was filling out paperwork. I explained that a wedding was going on and asked him if he could turn off his engine. He just said "I'll be leaving in a minute". Sure enough he made noise for another minute and then left. On other occasions I've always gotten similar responses. When I ask drivers if they have some company rule requiring them to keep the engine running, I just get a blank stare. But never once have I been able to get a driver to turn off his engine for me. It's almost always "oh I'm about to leave".
Once I found a tow truck that was idling near my house, and it was empty so I climbed inside and turned off the engine myself. It was pretty easy, just like with a car - just a turn of the key. Then a few minutes later the driver came by and turned the engine on again. Then he sat in the cab checking his smartphone.
If the engine only takes a fraction of a second to turn on and off, why have it idling even for 30 seconds, let alone minutes? It doesn't make any sense to me, but the behavior of truck drivers is so uniform, and often seemingly stubborn, that I feel I must be missing some principle which explains it.
(Originally posted at outdoor stack exchange)