Comcast ran out of RFC1918 addressing to manage all the devices on their network (think cable modems/set top boxes/routers/everything) and had a massively segme

Comcast ran out of RFC1918 addressing to manage all the devices on their network (think cable modems/set top boxes/routers/everything) and had a massively segmented network setup. They rolled out IPv6 because it flattened that network again, and instead of worrying about being in the right segment for reachability everything now gets a globally unique IP address. It massively simplified their internal management.