rustic, ill mannered
俚 centers on a lack of refinement: rustic simplicity that can tip into coarse or ill-mannered behavior.
俚 combines 亻 (person) with 里, which likely contributes the sound. The exact historical development is uncertain, but the character is associated with rustic or unrefined people.
A person 亻 from the countryside 里 is rustic and sometimes ill-mannered. Picture a villager who doesn't know city etiquette.
For リ, imagine a rustic person who is really ill-mannered: really -> リ, and their behavior is coarse.