I'm watching this show on Netflix and love it BUT all season 2 the characters kept to referring to each other (or themselves!) by their first and last names. Maybe it was because I.m binge watching it but oh.my.goodness it is annoying and distracting. Why do writers do that? In real life, when I'm talking to friends about a mutual friend first name is more than sufficient! Silly rant over now. ?
Part of it is just a quirk of the townspeople, especially in the case of Lavon referring to himself in the third person, and almost always his entire name.
Beyond that, I really think it's a CW show thing, honestly. Because they do it on The Flash, I've heard it on Arrow, and I think there's another show I'm forgetting where they do it. I also hear it a lot on soaps. So it's not something only HoD does, though believe me, you're not the first person to notice/ask about it! :)
One Tree Hill was known for that as well. Maybe it's a southern thing. I'm in Texas, and we do it from time to time. Kind of depends who it is, though.