I find that Google posters are more technically incline. Most of the people I circle are tech types or something else I find cool. I've also noticed that most people post to circles and not public. I will see people commenting on posts, but when I click their profile, they are sharing nothing.
My guess this has to do with them being more technical. Companies and everyone else are searching the Internet to see what you do online. If you don't share your post with them, they can't see it.
As for G+ being dead. I don't see it. G+ only allows 500 comments per post and I see maxed out post comments quite often. (very annoying Google, fix it!)
I suppose if you are an outsider looking in, it could look like a ghost town. Especially if you are choosing random people to follow. A lot of random G+ers don't want you seeing what they are posting.