Do you also leave your front door open (not just unlocked), so that someone can come take a piss in your bathroom and maybe read your mail and take your TV while you're at work?
See, it does not really hurt me if they use my network, other than bandwidth. That is why I want to be able to monitor what they are using -- to make sure that they are not *ab*using it. But you know what? Screw it, this is stupid. I am just going to secure the thing and get it over with!