@Aldarion Interesting topic. I'll toss in my two cents....
I believe Tolkien took great pride in presenting the big picture. His vision for Middle-earth was grand. He sought to present major themes regarding culture, government, and theology and then delve only into specifics in certain areas. For example, Tolkien presented us with the major themes of friendship, family, and language... and in the area of language he gave details (hundreds of words and working alphabets) on the workings of Quenya, Sindarin, and Adunaic.... while only teasing us regarding Hobbit-ish (Hobbit-ese... if there is a real name, it has escaped me), Khuzdul, The Black Tongue, and
Rohirr -ish (Is that a word?). He gave us no information on the wedding and funeral rites of the Shire, but gave us more than enough information on birthdays.
Obviously, he was greatly intrigued by alphabets, calendars, birthdays, and songs/poetry.