Google+ is like teeing off at Augusta National - you never know who you're going to meet until you get there, and when you get there it might be a tad 'stuffy' hanging out with the same group of people. This velvety-red rope exclusivity type of social media just doesn't work in its present form. People just want to be in a 'room' where everyone else is...I mean, I want to know what my ex looks like and I sure hope my ex looks at my photo and see what's she's missing. =) You can't show off to those that you want to show off at Augusta National when those people you want to show off for can't get in...
Answer: People didn't need another Facebook. They already have one.