Why do we say "hello?" when we pick up the phone? We ask it. Why? Are we honestly curious as to whether someone is there or not? I'm pretty sure if the phone rang that someone, or something, had to make it ring. In most cases I find it strange that we cautiously approach greeting the caller as if we're afraid of being rejected by silence. But then again, saying "hello!" is somewhat strange when we don't know who's calling.
Social norms are weird.
