This moon's face is a personification of the moon, much like the Western "Man in the Moon" story. So, beyond just indicating nighttime, it can also give a friendly feeling, as if someone is watching over you.

Unlike other moon emojis (🌕, 🌘), this one is used as a symbol of a positive and peaceful night thanks to its uniquely gentle expression. In Korea, the moon is affectionately called "dal-nim" and seen as a friendly entity to make wishes to, and this emoji captures that warm image well.