What are ALL the legit reasons for idling on city streets (including small vehicles)?

Hi all, COMPLETELY ignorant about trucking here, I've never been a trucker or CDL holder, just a regular license holder; you may also see that my terminology is all wrong; please forgive that.

My question is not limited to trucks. I hope that's ok; I figured this audience still might be the most knowledgeable.

WHY do so many vehicle operators leave their engines running on city streets even when they know they're not going to be moving their vehicle for at least several minutes, sometimes much longer than that?

Of course I am aware of some reasons: in order to keep climate control working; in order to operate some connected equipment that needs engine power; in certain 20+year old vehicles, starting the engine uses more fuel; to indicate to a traffic cop that the vehicle is only stopped for a moment, etc. I'm trying to find out the reasons I'm NOT aware of--and again, about all kinds of vehicles, if possible, not just the trucks normally discussed on this forum.

Let me give a few scenarios I've witnessed and ask if you can explain why that driver might have been idling, and maybe these examples will remind you of others you can illuminate me on:

-Crew of a van doing some work in a nearby building; they're moving stuff in and out of the van. I can't see any reason they need the engine running, but they've put chocks around all the wheels and have left the engine running. It was a very new looking van. Why?

-Guy sitting in his new SUV in an on-street parking spot. Engine idling; I figure he's just waiting for someone and didn't feel like turning off the engine and turning it back on again. But then I finish my hour-long errand, and when I come back, the guy's still sitting there, reading, with his engine running. Why? Legitimate reasons you can think of?

-Drycleaning guy makes a delivery from his van. Leaves the engine running, puts it in park, hops out, goes into a shop for two minutes, comes back and drives off. Van isn't more than 10 years old. Why? Is it really just because he doesn't want to go to the trouble of taking out the keys and putting them back in?

-Guy goes into a 7-11 for a pack of cigarettes. Leaves his engine running in the parking lot, with his key in, window open. I used to see this one ALL THE TIME. Why?

Finally, I guess I should point out that while I'm sure you could dream up reasons that are unique to those scenarios above, but I chose those examples because they're typical of what I see *all the time*. If you can inform me as to why practices like the examples above are so incredibly widespread I'd be very grateful.

One last thing that might help narrow your answers: can you rule out this silly hypothesis I've had for years? Do a significant number of people do this JUST BECAUSE THEY'VE SEEN OLDER OR COOL PEOPLE DO IT? Seriously. Forgive me if that's the most ridiculous part of this way-longer-than-expected inquiry, but I'm really curious about this; have been for years. If you can educate me about this I'd be very appreciative.