A lot of spiders have spread with humans and, depending on your environment, would probably not be able to survive outside. I usually ignore spiders I see in my house. I figure for every spider that's probably at least 3 less other bugs. One time we even let a daddy long legs care for its babies and watched as the hundred little eggs finally matured and hatched. Most of those babies probably died, but those that survived have probably helped keep the population of many other bugs down