I think INFJs become directive mostly with people they care a lot about. They expect more of them because they make up a big part of their inner circle. They also don't tend to risk conflict unless they believe that it needs to happen for the relationship to continue or because it is fueled out of sincere concern. And in some cases, if the person they are extremely close to acts in a way that is extremely far out of line with the INFJ's beliefs of what is good and right, they may not be able to co-exist together. Casual acquaintances and friends don't really warrant that kind of emotion, trouble, or risk of damage to the relationship.