As you say, roundabouts take up more space, and they are not nice for pedestrians. They're good for major interchanges if you don't want to build an underpass

As you say, roundabouts take up more space, and they are not nice for pedestrians. They're good for major interchanges if you don't want to build an underpass and there's lots of land. If land is cheap though, where are all the cars coming from?