What does face to face interaction have over online conversation?
Non verbal communication may be overrated, but here is something favoring face to face interaction that most people wouldn't think about. Something I would call the "captive audience effect." When folks meet in person, there are usually not that many people in the situation. A room full of people is pretty limited. Folks in a small group setting are usually forced to hear each other out versus scrolling on. Maybe "forced" is too strong a term.
On the internet, there's a lot more choices. There's information overload so people can just swipe to the next and to the next down the line. In a smaller setting, interactions are often a bit more focused and in depth. There isn't as much information bombarding the situation.
When you meet someone in person, you are sometimes surprised to find the person more interesting than your first impression. Online, your natural filtering works differently. For instance on dating sites, people often filter via numbers such as age, weight and so forth. In person, the stats seem to be less absolute.
I'm sure there are some cases where online interaction can be more in depth than in person. One problem that both online and face to face interaction have is distraction. Conversation and focus is often interrupted with distraction, in both cases.
In the big and fluid world of online, only a few household names rise to the top; like there's only one Facebook, one Google, one Amazon and so forth. In the brick and mortar world, lots of little outfits can survive as they serve their more limited geographic areas. The captive audience effect. With the whole world at one's fingertips, only a few household names, like Amazon, can rise above the fray of voices from millions all over the world. In the brick and mortar world, that fray is more limited. In the quieter fray that just comes from a limited neighborhood, more names can rise to the level of being noticed. More can be noticed even if they aren't "top in the world" as they aren't competing against the whole world.