I mean, it's pretty easy to understand if you just look at motivations. For most people who own a house, it's a pretty big part of their net worth. Nobody wants the value of their house to go down, and if you allow construction of more housing that is what will happen.
Local council members fear geting voted out if they make constituents unhappy.
We need both sides to think of the good of the community as greater than their own financial/power interests. But that's very hard to actually do.
