Google is trying to boost Google+'s social network with attempts, which have not been done before, blurring the line between users of Gmail, Google Maps and other Google services. If you sign in to any of these services, that means you're signed in to Google+.
Leaving aside other issues, Google Hangouts is clearly a superior technology. Previously, Gmail video chat was often echoed and sometimes abruptly escaped - just like the previous video chat quality of iChat. But now, FaceTime of Apple, Skype or Google Hangouts is different.
Hangouts are much bigger, making it easier to invite new people to the chat session. Sound quality in long distance is also very good, making Hangouts the best choice for companies who need to translate many free video voice services, replacing remote conference services through systems like Telepresence. Cisco.