JLA Cyberforce pg46 Wonder Woman

Diana and J'onn's tete a tete continues. He explains that he had to come back because his wife asked him too, explaining to him that his 'life song' was incomplete and "we would hear more if you can bear it...for it fills us with joy and pride to watch you sing your life..
Last panel "...Now go home, J'onn and Sing"
And that's why J'onn came back.
I bet his wife didn't know it'd be Diana waiting to greet him with open arms when she said that though....she probably had Superman in mind...or Flash,