>In other words, some conferences are built around creating a network in the hallways. If you take them online, there are no hallways.

There are no hallways. Also, there are no side conversations, serendipitious encounters, forming and disbanding groups naturally, after-sessions social activities, or meaningful ways to gauge attention or intuitively navigate turn-taking. There's no forcing function of being in the same time and place among people of similar interests.

Online is fine for content delivery, so presentations and slides easily transition from in-person to remote. However, the medium doesn't conform to how people make actual human connections. Online events can be deeply frustrating because the social instincts we've honed since childhood are suddenly useless in that context.