Why? Because a router only gets you passed the 5 device limit; it does NOT get you additional bandwidth. I have a 10 year old that, although he does stream YouTube from time-to-time, needs to have reliable internet for school and I don't want my viewing behaviors and multitasking via our Surface tablet and our cell phones to interfere with his productivity. He loves Minecraft (I still don't get it). The Windows PCs in the basement will be on the router with the Mobley so I don't have to download all Windows updates twice (or more), they can share with each other.
School is a whole lot different than when even I was in school. $45 gets me two unlimited APs, with two separate SSIDs, two separate IP schemas for half the price of the data capped, weather-affected Exede.