Well the Dreamers still remembered, though they didn't know it, and once people were fixed they were sent back to wherever they'd come from. No one really thought about it much, I know I didn't until I got here, that how could we get new people and lose old ones if all roads led both to and from the Village.
That and Dreamers had a way of disappearing if they started to talk about what was outside, because, of course, there was nothing outside.