Actually, some do.

I have done something similiar (blocking access to various websites (*.google.com, *.battle.net, *.yahoo.com, *.ebay.com, etc.)) to an unsecured router with the defaut login I found using wireless (it was a Netgear router I believe). I didn't go so far as to change the password, but I'm sure it took them a while to figure out why "the Internet was broken".

An unsecured wireless router, broadcasting its SSID, and using the default admin password is just asking for trouble.