It's a question of expectations. The people who are active on G+ are ones that like to engage in conversations, particularly with people they don't know. They want to talk about emerging trends, technology or business with like-minded people. But for the majority of the population, they don't necessarily want to engage with people they don't know, they want to engage with people they do know. And in that aspect, for now, G+ isn't where it needs to be.
I see a lot of promise in G+, and when more of my friends and colleagues begin to actively use it, I will be more prominent on it, but for now, it's even less valuable for me then Twitter because there isn't enough of a critical mass in the areas that interest me.