Routers have "line-of-sight" limitations. These are distance limitations without obstacles. However, when you add in steel girders, steel reinforced concrete, walls, appliances, and other electical devices, they all combine to create barriers to reception. Therefore, boosters, or additional routers are necessary to retain signal strength. These can be controlled and operated without licensure while generating income for their use. On the other hand, you're generally right. A signal tower would be less complicated. You would still have distance limitations, and boosters may be required. But it may be monopolized by an entity that would require a subscription and payment for its use. In that regard, it could raise prices at will without fear of competition. It also centralizes control and represents a part of the "big brother syndrome" that alienates people.