Because here is Google, which owns my email (gmail), my RSS feed reader (Google Reader), the RSS feed from my blogs (Feed Burner), my search history (just plain old Google), my news sources (plug-ins in iGoogle), and a pile of other stuff like Google Maps, YouTube, Google Books, Google Translate, and so on, none of which appears to be connected in any unique way to Google+.I fully agree. Right now even Google Buzz is more useful to me than Google+, because Google Buzz automatically "streams" my blog posts, and Google+ doesn't. I'm currently also spending a part of my time on Facebook again, because Facebook has games, and Google+ doesn't. The only thing Google+ does in abundance is telling me that other people added me to their circles, which I usually respond to by adding them to my "following" circle.
If that doesn’t say something about Google, I don’t know what does.
For me these social networks are platforms. A platform all by itself is rather boring. There needs to be something happening on that platform. Personally I prefer games, but it could be something else as well. Being an extended Twitter with the ability to share photos and videos is probably useful to some, but I don't think this is the killer application yet.
[EDIT: While I wouldn't say this description is in any way not correctly describing Google+ in its current form, some readers let me know that there are unconfirmed rumors of Google games being in development for Google+, with a logo found in the source code, and Google having invested $100 million in Zynga.]