User blog comment:CamperThirteen/Witness my caffeine-induced stupidity/@comment-1324135-20091216024120

Because she's Supes' wife! Or girlfriend in some adaptations. He's head over heels for her in most of the comics and stuff. However, I think it really depends on the writer, since apparently in a couple of comics Superman/Wonder Woman is full-on canon. There's even one or two where they get married and have a child, and that is enough for me. :D