People who are more reserved and less “people people” have more of an intellectually guided behavior. They utilize a measure for judgement that has more of a rational appeal, i.e. an ideal or system they deem to be fair. Law is one common system, a religious based moral code may be another. Whatever system you use to judge other people you also use to judge yourself, thus it follows that someone who has this sharper focus on law-abiding behavior would be more aligned with laws.
On the other hand, outgoing “people people” tend to utilize a relationship-oriented measure, a more fluid image of what they believe good, sociable behavior to be. Laws can seem cold and harsh, and put serious strain on relationships. This results in a softer internalized code that isn’t totally anarchistic, but is willing to stretch laws because it allows them to empathize and associate with more people. While this might pull one individual down, it will also pull others up.
Your reserved individual pulls themselves and their smaller social circle closer to law abidance, while your people person is more of an average of their larger social circle. The former behavior can be alienating, the latter compromising.
Both this article and the “how to train your extrovert” article mentioned display a bias towards the more reserved behavior and against relationship-oriented behavior. The very notion that people with internal strength should influence others implies they need to build additional relationships of high quality — no one listens to “that friend” who is always quick to issue critical judgement.