It's not even just that, given his response to the fans at the end of last season I suspect he thinks he's doing a good enough job. In fact I think the board feel he is doing a good enough job even after last season's debacle.
This is the problem...Wenger seems to set his own standards of what constitutes a successful season and they are not always consistent and certainly don't match up with a sizeable percentage of the fans ambitions/standards.