So in law school when do people often act like "don't know" you when walked by?

So I noticed in my law school most law students act like they don't know you and pretended they don't see you when walked across you, especially among girls and guys, and I'm like, come on, your parents didn't teach the basic manner stuff? Is it because they are mostly 25 years old and are socially awkward with some degree of cockiness and arrogance thinking they are prestigious?