He already answered this in an interview about the Social Network. A lot of people in Hollywood (and in general) don't understand the concept of just loving to

He already answered this in an interview about the Social Network. A lot of people in Hollywood (and in general) don't understand the concept of just loving to build things. Facebook was built by him and it's gotten insanely huge and when you've dedicated a large portion of your life to something like that, you don't want to give it up. No other work would be satisfying; facebook is his. Some people truly love doing this stuff and don't build it to flip it and that throws people off