I'm in a metropolitan area and see them from time to time. They're usually chatting with each other, not bothered by any "interested persons".
I assume they believe they are giving a "mute witness", like rocks NOT crying out. Or maybe they think they are somehow relevant by being there with a trolley. Looks like an easy way to count some time. For a supposedly "life-saving message" with "end coming soon" urgency, it all looks very boring and lazy.