Chalk boards are very visceral, Bringing a chalkboard instead of powerpoint when giving a presentation, makes for a much better presentation, A whiteboard is almost as good but does not have the same impact as a chalkboard.
While I agree in principle, I can tell you from extensive first hand experience on both sides that it's extremely easy to lose the audience with math heavy content on a blackboard too.
The only thing that I found to be really useful is for the students to already be familiar with the content (having actually prepared for the lesson), and the live session only reviewing it and then focusing on the deeper or most confusing parts.
Of course - what also helps is that writing speed with chalk is somewhat slower than writing speed with pen & paper, so that gives the audience some opportunity to catch up.
