The real reason they want this is 2 fold
1. Money. it is always money. They want to be able to advertise "Internet for only $30" but then tack on 20-30 in "other fees" to get that bill up, $5-10 for a router is an easy gain
2. Control. Companies like comcast have lots of control over the endpoints to the point where they can manipulate the firmware do do what ever they need for traffic management or even offer public wifi access to all your neighbors...