Your house is the unnatural thing that doesn't belong, not the spiders. They existed before we built houses. They exist in the world whether your house does or not - your house is what trespasses the spiders' territory, not the other way around. It also isn't their fault that big dumb apes built structures that they can get into (and that is usually beneficial for them to do so, being dry and mostly free of predators), then decided they don't belong there.
Plus, speaking from experience having had many mama spiders in my house, they don't "take over" - they find their way outside. Unless your house offers an abundance of their food source (bugs) inside, they have to go outside. They go out the same way mama came in, and they do it fast because they starve to death otherwise.
Imagine if we killed anything we wanted just because we were afraid of it or just thought it was icky - oh, some people do..........