A backsplash in the kitchen made out of those linear tiles in shades of grey, or at least that’s what all the house flippers of the last few years seem to think.

Minimum dollar value for the house.

Higher taxes I imagine. Government only has so much land to get money from so they want the most money per unit. You might say “well why not put an apartment building there?”. Which should mean even more money but each person there is a certain cost. So even if you make more money per unit you spend more. The ideal, from the POV of the government, would be the town having no residents only businesses. Plus you know only poor people young people and non-whites live in apartment buildings and Karen on the zoning board has strong opinions on those types.

Basically bigotry and incentives.