Whenever I encounter them, it's in a smallish neighborhood and they seem to be trying to keep some some sort of small town/country feel ( big lights have that city look or something). Or maybe too cheap to buy the traffic lights? Don't know.
First world problems: did a wet install of a screen protector (something always goes wrong when I do these), and the installation seem to go great (Great product by the way, from "IQShield"). Then at the very end, as I was squeegying and smoothing everything out, my finger nail dragged along the screen protector and just gashed it Moral of the story: Always cut your finger nails before installing these things. Neglected that for too long. Eight bucks down the drain it seems... Or not... hell yeah I'm going to use it even with that gash across it!
They're used at complex cross-sections, i.e. ones with more than just a 4-way intersection, to prevent accidents. Here they're called traffic circles, and I've used them successfully. The one in the image is unusually complex, with smaller circles within the larger one. As for small towns: I've used them both in Boston and in small towns here. You've never been on one, boone?