Probably comes down to the unwillingness of US legislators to create clear laws. Too many compromises to satisfy lobbyists and avoid any negative campaign they might sponsor. Judges likely do the best they can trying to interpret the mess of case law they depend on in the absence of modern legislation. I have no idea why the US supreme court gets to decide on matters like abortion based on hand wavy interpretations of historical documents when in any normal democracy the politicians do the will of the people and enact legislation that reflects modern society.