You don't necessarily want to hide from everyone, just from those that have no business peeking into your home. Just because you don't want your internet provider to know everything about you doesn't mean you want to hide from the communities you're a part of. On places like TMO where you share only a relatively small amount of personal information, you're just a username, mostly disconnected from your real life, so you don't really lose any anonimity by logging in.