A group can agree to meet without agreeing on what the meeting means.

People can agree on the appointment and disagree entirely on the meaning of it. One person is coming for a proper conversation, another for a distraction, another out of obligation, and the mismatch produces disappointment that nobody can locate afterwards. The logistics were shared and the purpose was not.

When a gathering matters, saying what it is for takes one sentence and prevents most of this. A catch-up, a celebration, a chance to talk about the difficult thing: naming it lets people arrive correctly. Left unnamed, everyone brings their own version and at least one of them goes home feeling that something did not happen.