Why Google+ Exists
1. Because Google Wave Couldn’t (Exist)
Good design is apparent. There is no need to explain the function of a well-designed product or service.You look at it and you know what to do with it.
Google+ exists because Google Wave couldn’t.
Google Wave couldn’t exist because it was a poorly designed product/service. We know it was poorly designed because it’s Developer’s (preview) introduction video was 1.5 hours long. To put that into perspective, the Mac OSX Lion preview was essentially 1/3 of what was a 2 hour WWDC 2011 keynote speech (granted it was 10 key features of Lion, still, a developer preview [or any type of preview for that matter] should stick to its self-definition: a preview).
Even the more consumer-friendly 2-minute Google Wave promotional video is mired in an arguably speedy-conceptually-esoteric framework.
2. Because Facebook Exists
The reason why we know Google+ is designed well is because, when we look at it, we know what to do with it. We know what to do with it because it practically mirrors Facebook, which we are all pre-disposed to. This is a case where we know who the chicken is, and who the egg is.
No Facebook, no Google+
Yay competition!