Well, it isn’t always online, so the question is irrelevant. It just starts online by default because, generally, you have an internet connection. You can go offline at any time by going to the main menu and selecting Logout.
Yes there are times when we don’t have one, but in this day and age, it is increasingly uncommon. Thus why would you want to not have access to your friends list and such when you have the connection there for it?
I’m legitimately tired of the paranoia surrounding games being online or connecting to the internet. I basically never not have the internet unless I have a power outage. I really don’t care about stuff like this provided it isn’t interfering with my ability to enjoy the product. Since there is indeed an option to go offline, I am unconcerned.