As of now, Google+ and Facebook remind me of ICQ and AIM.

I used to only use ICQ. I tried to avoid AIM, but then ended up joining to chat with a girl I was interested in. Turned out most of the non-tech/engineer world was also on AIM, and over time AIM won out as my chat client of choice.

So my suggestion to the Google+ team: find a way to get girls to join!