Not because of his morally-foggy anti-hero bad-ass character portrayal in that scene (as film nerds claim), nope it was simply because Greedo was distracted by being "at that time of the month" (apparently ;) )
(https://scontent-ord1-1.xx.fbcdn.net/hphotos-xft1/v/t1.0-9/11407284_10103211780657828_4003390466648069589_n.jpg?oh=88c163b2e25e99ca5738aed5329e82c7&oe=5633EF23) (https://www.facebook.com/photo.php?fbid=10103211780657828&set=p.10103211780657828&type=1)
via a comment @ Pete Mayhew's facebook "This should settle the Original story of 'who shot first'..." (https://www.facebook.com/peterangie/posts/10153894976828998)