So what happens in other locations is that demand for locations starts going up, housing prices go up, taxes go up and people who can't pay those taxes get displaced. Developers buy those houses, raze them in favor of apartment complexes and eventually you get density.
If people can stay in their single family 1.5 or 2 million dollar homes and pay property taxes on the 30k they bought it for 30 years ago density won't happen because those are the people that vote and they'll keep voting for municipality limits on building to "keep the character of the neighborhood".