Better then when the business won't show up on maps, unless you type the name in. There are a ton of businesses that even if I zoom all the way in on that business it will not show the name of the business. But if I type the name in it will show in the correct place. It's annoying as hell. I know there is a certain business there. I can see the building in maps. I just can't remember the exact name. I need the phone number to know if they have a part or an item. Have never been able to figure out why Google maps and Apple maps does this crazy stuff.

Did you search for them at some point? In my experience you have both random stuff popping up and past searches hits. I suspect the absolute random stuff ro be related to advertising.

I have a business registered on Google Maps as an actual place, and frequently get contacted by email asking if I'd like to pay to have it promoted

I've never used it but the option is there

Square icons are ads

Those are indeed ads.

I believe the business pays per click. I've seen (edit) only one estimate for the cost, claiming $2 to $6 per click. (https://www.shopify.com/retail/google-maps-ads)

(I previously had mentioned a second estimate but that was for regular ads)

The ones that want your clicks are obviously advertisements.

But I see a lot that have nothing to do with clicks, and I think Google is just testing to see if it's irrelevant location... Showing it to a small number of random people and seeing if they click on it.

It's probably because you are zoomed in enough