At least in my area, 55+ housing is the only multifamily housing that gets approved for building, because it adds to the tax base without adding students to the school district.
Also, in one rather hilarious instance, a gigantic 55+ development is going up on... land that is too toxic to allow children to live on, because it was a mechanical gauge factory before WWII, and the ground is saturated with unremediated mercury and other toxins.