Yes, it's you being both ignorant and american. This argument quite directly, without any slopes (slippery or not), extends to for example acquiring a piece of land, building some housing at premium costs and then slapping a factory (and waste landifill, for a good measure) on the rest of the lot.
Housing regulations exists for many abundant reasons. Living quarters vs short-time rentals drastically change requirements for and load on surrounding infrastructure, which is built out based on established zoning.
Between zoning, easements, nuisance laws, government has a lot of say in how you use your private property. Owners even stepped it up a notch and invited HOAs, a quasi-government that has even more say about your property.
Unfortunately, people love telling their neighbors how they should live.