People who do not observe the social norm also known as "the buffer zone."
Example #1: If there are three stalls in, say, your workplace restroom and you take the first one because, hello, everyone knows that it's the least germy, should someone enter after you, they should always take the stall on the end, thus allowing the middle stall to serve as the buffer zone. This allows for what little semblance of privacy remains when sitting in a room with another human while your pants and undies are around your ankles.
Example #2: Should a movie theater be nearly empty and you happen to be sitting in the back row near the middle, the next patrons to enter should, under absolutely no circumstances, sit directly next to or in front of you. Furthermore, as the theater fills up, there should be at least one seat between you and and a patron with whom you have no relationship whatsoever.
Hello, social norms. Observe them.