> "why don't they need one to get into my "facebook home"?
Because there is no such thing as your Facebook home.
If you're associating Facebook with "your home", they have you by the balls. Google is trying desperately to grab your balls too, so that your Google profile is the center of your online persona. They make incremental, subtle changes to push users towards Google+ to achieve this. The latest change happened this week, where you can no longer have a profile picture on Youtube unless it comes from Google+. They actually removed my profile picture, and popped a message up saying I have to go to Google+ to set up the profile picture again. They replaced my avatar with a generic blue pattern that looks like crap. Bastards. I don't want a Google+ profile. I don't like being forced to use social media services just to have a profile picture on Youtube, or just to rate an app on the play store.
Your "home", digital or otherwise, should be under your control, not sold out to a company. IMHO there needs to be new laws designed to protect our "digital homes" from the very tech giants who facilitate them and change the rules at their choosing, absent user preference and input.
Imagine not being able to get into your own house without first logging into Facebook? Or not being able to use the internet without first checking in with Google? Far-fetched? Not really, it's slowly heading that way in baby steps. The needs and wishes of companies and government first, citizen freedoms and user-control and true privacy second or third, or not at all.