An appointment is involves two or more people agreeing on a time and place. Meaning people actually have to ask for the other person’s time of availability.
An appointment is not your free time. So when we say we set appointments, it usually involves asking the other person when they are free and where they’d like to meet with you. Merely sending a declarative statement about your free time is not setting an appointment. For an appointment to be set, people (yes, that’s plural) actually have to agree. Meaning, you have to deal with an entity other than your self-centered self.
Simply put, it’s NOT just about you.