A potluck requires everyone to bring something to the event, be it food, drinks, or supplies. There’s infinite possibility and creativity. One can make their own food, or one can buy food. One can bring a main course, a side dish, dessert, or soup. One can even bring multiple items, or none at all.
Everybody brings a part of themselves to the event, in addition to themselves. Participation is built-in. And when there’s participation, people tend to be more engaged.