The same thing happens in suburbia. People don't look at city plans, thoroughfare plans, zoning (current and planned), etc. Are people seriously not as big of nerds as the rest of us?
People buy a house in the suburbs that has a ROW for a six-lane road on one side and then get pissed when their "greenbelt behind their house" suddenly has a road. But when I bought my house, the first thing I noticed was there were some large plots of land around our neighborhood. I wanted to know what was planned to go there or, at least, what zoning changes could potentially happen down the road. You can't catch everything, but a lot of stuff is available when you take time to look.
Re: downtown/urban environments, density and development is part of the package. There are trade-offs, but you have to realize that going in.