They want the riff-raff to get the numbers up and lure people away from facebook. Someone's friends have to move wholesale or they have to be prepared to use 2 SNs until most of their network is on G+.
I really like G+. It's way better than facebook so I want to use G+ instead and there's enough twitter like functionality that I may stop using twitter. What Google need to overcome is facebook's momentum.
I have around 35 RL friends on facebook but only 3 have come over to G+. They're the ones who don't mind using G+ and facebook and twitter or don't have enough invested in facebook. Another 2 are on G+ but don't use it because the rest of their friends are on facebook and won't move over (I remember the comment of one such non-techy person when G+ was mentioned: "Who cares?"). I've already stopped posting to facebook and only go there now to comment of friends posts. I've made the decision to use G+ and if my friends don't want to move with me then sod them.
As for the celebrity thing, I can't understand Lady Gaga (I barely know who she is) but some celebs are worth following. Steven Fry often has something worth saying and I can find out what he's doing (new series of QI etc). I've been able to engage with some minor celebs of twitter so it can work as a tool to break down the barriers between celebs and us "normal" people.
The bottom line is, Google should do whatever they need to do to make G+ a success. It's not like I have to ready the inane ramblings of the celebs or riff-raff so I don't mind.