Have you ever done a white boarding session where more than one person was writing on the board at a time?

The online whiteboard works great when one person is adding to it and it's easier to read (you don't have to deal with people's terrible handwriting) and you can save it.

In most cases I've found that only one person is usually writing on the whiteboard, everyone else is just pointing at it and making suggestions. So the one person with an iPad that is sharing it's screen is usually more than sufficient for online white boarding.

The rest of it you're right, seeing body language is helpful, getting a chance to hang out socially is helpful. But not helpful enough to outweigh working from home given that I already have a social circle.

If work were my social circle, like it was when I was younger, it would be a whole different story.