Many people who may steal data would never dream of breaking in and physically doing it.
It is much easier to steal 1s and 0s than it is to physically do it. Humans seem to take the path of least resistance. If they can do it, they will do it. And if they won't do it on their own network then a bad guy from Latvia or somewhere who knows how to send phishing emails will.
Due to the mystery about who is truly on your network combined with the ease of breaking bad security, you have to protect yourself fully. Banks don't have lax security just because people 'shouldn't' rob banks.
Sorry blogger guy....your argument just doesn't hold water
edit: I want to add the reason your house is insecure is because we can't protect it with math. If you wanted a perfectly secure house....you would end up sinking billions into it and end up with a military base. Locks are flawed, Windows are flawed, but they are good enough so that when there is a security breach you will be aware of it and can hopefully remedy the situation or fight back.