I think Yakov wanted to start his own life. I mean at this point in the story he had a rich company, a huge family. His whole family lived with Laban and did not get to see the world so Yakov probably wanted his family to have a life of there own. Also Laban had lied to him so many times i would not want to be working for him. When Yakovs last deal with Laban was fake when Laban sons took away his flock he probably was pushed over the limit and left.