In cold climates the sewer and water lines have to be buried deeply. As the builder brings heavy equipment in to dig holes to lay those lines it is a small matter expense wise to continue digging a hole large enough for a basement! In our Valley of the Sun we do not have deep freezes. Our water and sewer lines are about 18 inches below the ground. Our footers are not much deeper. Our homes are mostly built on cement slabs. There is no need to bring in heavy equipment to dig deep holes. If they do dig that hole and create a basement home, they will have to include a “pump room” with a pump to get the water and waste from basement bathrooms and sinks up to the level of the sewer lines. If you have a “pump” room, you may need the assistance of professional plumbers to help maintain your home. Many plumbing companies similar to this plumber https://callstevesplumbing.com/plumbing/trenchless-sewer-repairs/ can help assist with things like sewer and drainage problems.We do have electric outages here as in other cities. If you purchase a basement home you accept the possibilities that come with power failures.