I believe that biting, in the case of Suarez, is a purely animalistic behavior. Young children often bite as a means of instinctive attack, using what is considered to be their most effect weapon. Adults, on the other hand, are only more likely to do so when put in an extreme situation as means of defense. Deep down, we are all just animals running about wearing rags and drinking coffee.
For Suarez, I think his passion towards winning or overcoming an opponent boils inside of him to a point where he almost has no control over his actions and lashes out. It is sad, despicable and almost admirable. He places so much importance on personal victory that he is unable to contain a primitive and deep-rooted response to adversity. The bloke loves the game and loves to win- but at the same time he is a vulgar little beast with no higher consciousness than a snappy terrier.