Who else will be there?
That's what determines, for most of us, whether we will show up for the party or the conference or the meeting, especially when we have a choice.
This also gives us agency as the impresario to design our projects with intention.
People mostly seek affiliation and status more than anything else. When we see ourselves as belonging to the group, we are much less likely to say no. And if it's a group we aspire to be in, we are going to say yes.