A satellite is capable of covering a third of the earth. The larger the footprint, the more diffuse the energy that's coming down from the satellite, which means the less powerful the signal is.
So again I'll use the flashlight analogy. Ideally, there's sort of a trade-off. You want to cover large geographic areas, but you also want your satellite to be reasonably powerful. The more powerful the signal is, the smaller the dish on the ground can be that's receiving the signal. That's important if you're providing direct-to-home satellite services. You don't want massive dishes hanging outside people's balconies and whatnot. And the more powerful the signal, the more bits you can get through that signal, the more throughput you can get.