I see "free social interactions" as neither a benefit nor something that can only be obtained on-site.

These "free social interactions" are often just distractions - taking you out of your context, making it difficult for you to be productive.

That's why I love remote + Slack. Slack is async. I can finish what I'm doing before addressing messages there. On-site, people rarely if ever warn of their intention to come talk to you - they just walk up and start talking.