Where I'm from it's exactly the opposite - straight road means you can't trust drivers to slow down, but any obstacle like a big mound with a road in a circle around it makes them pay attention
I would love it if roundabouts caught on in the states, at least the single-lane ones. Multi-lane and the huge ones with traffic lights always scared me when driving in the UK.
Roundabouts aren't great for pedestrians. You need to trust the drivers' signals.