That's a very good point.
Our city is rapidly growing and the population is moving eastward. The developers in the east part of town here have an unhealthy obsession with roundabouts, as they put them in about every 20 feet in a very busy area with lots of shopping/apartments/offices plus a major hospital (it's interesting to see ambulances and fire engines fly through 3 roundabouts trying to get to the hospital). I've almost been sideswiped more times than I can count because people think they can come into my lane/cut me off while I'm inside the roundabout (the roundabout is divided into 2 lanes, one for turning right or going straight, the other for turning left or going straight). They also miss the big YIELD signs that are posted just before entering the roundabout and just floor it through even though there are cars in the roundabout that have the right of way. Sometimes, I swear I can see my life flash before my eyes when going through those!
It would seem like it's not that difficult of a concept to get. They have arrows on the road telling where each lane is supposed to go, a couple signs showing how the roundabout works, and big yield signs saying when to wait for cars. But alas, people still don't get it.
We also have a "diverging diamond" intersection that the city thought would be an excellent way to cut down on traffic accidents at a busy intersection. They were right, it did cut down on accidents at the intersection- except it also increased traffic going through the residential area that surrounds the intersection because people try and find ways to avoid the whole thing. Which has then caused a number of accidents on the other streets.