A more casual one with friends? We can be across from each other or even a few seats away as we see each other all the time. It makes it easier to socialize with friends we may not see all the time.
Large family gatherings? If at a restaurant, we are either next to or across from each other - makes it easier on the wait staff for the checks.
Large family gatherings at a house? It doesn't matter as we're all socializing with family members. Take for instance my family reunion coming up in a few weeks. We are staying in a (large) cabin with roughly 20 other family members. I don't care if I sit near my husband there, as this is the only time I see some of these people every year due to how far-flung we are distance wise.