A WAN is kind of like the road connecting houses and businesses and recreational areas. It costs to lay them down, and once it's done it's done, removing them and replacing will cost even more. The WAN's are owned by the ISP's. Once you are connected to a WAN and pay the ISP it's costly to switch over to another, because you need to replace your current cable connecting you to the WAN's. It's especially tough in rural areas, where there is often only one WAN owned by a single ISP. You'd need to pay another ISP to lay down a whole new "road" from one of their own WAN's in order to switch. Realistically, and depending on the distance to the closest bigger city, most people in a small town needs to work together to switch the ISP. It's just as if roads where owned by corporations. Therefore, ISP's almost have monopoly over a lot of their customers.