Well let me help you out.  If everyone knows that your router is located at a x.x.x.1 address that is one piece of information that they no longer have to gain to compromise the network.  Additionally, if x.x.x.1 is used DOS attacks can be made from

It really does not why should the security of our network be compromised by having to use any numbers from comcast.  This is why they are local area network addresses the key term is is local.