This might be the most underrated one.
You do not have to constantly think about how you look, whether your joke sounded stupid or whether you are talking too much. Around certain people, the conversation simply flows.
You can be quiet without feeling awkward. You can disagree without fearing a fight. You can say something silly without worrying that they will judge you.
And sometimes that comfort slowly turns into attraction.
Because while looks might make you notice someone, the little things they do can make you want to stay.