In a very real sense, most people do not even recognize there is an actual option to move. Yes, there are all sorts of costs associated with the moving and there is stress to be incurred as a result, but I think most people do not even entertain the idea of living anywhere else compared to where they are for numerous reasons including familial ties.
And then there is the 'why should I leave' aspect of it? Maybe if I stick it out, it will get better ( especially if I own that piece of land ).
In short, I would like to be able to say that it is economically prohibitive to do so, but, I dunno, I moved from the old country to US. And separately the moment I heard a first shot in my neighborhood in Chicago ( and police came to my door asking if I saw anything ), I was out of there in a couple of months in the suburbs.
I think people feel safer being where they have always been ( as unsafe it may be to an audience from a statistical point of view ). It is the environment they know. For all they know, anywhere else may be even worse.