If you thought that Google+ is just a divide service you can effortlessly disregard if you don't want to use it, you were wrong. In an interview with Steven Levy, Bradley Horowitz - Google's VP of products - says that Google+ is really Google itself.
Until now, every single Google property acted like a split company. Due to the way we grew, through various acquisitions and the fierce independence of each separation within Google, each product sort of veered off in its own direction. That was dizzying. But Google+ is Google itself. We're extending it across all that we do — search, ads, Chrome, Android, Maps, YouTube — so that each of those services contributes to our accepting of who you are.
Redesigning all Google services to match the Google+ interface is not just about constancy, it's also a way to show that they're part of the same super-service, an surrounding layer that makes them work together.
Google+ made Android's camera app put together with Picasa Web Albums, Google Talk put together with YouTube and Google Docs. It's probable that Google+ will make Google services more useful by combining their strengths. That's almost certainly the reason why you'll use Google+ even when you're not going it to Google+ and you'll end up joining Google+ even if you don't like communal networks.