That's a fair point, but I put a lot of stock in physical interaction. I suspect that being physically part of a class greatly reduces odds of drop-out, and improves group study.

(Of course, this is an empirical claim, and I can't say I'm basing my opinion on a published study.)

More cynically: some undergrads struggle to get out of bed for their midday lectures. They would not thrive in a MOOC, where there is less immediate pressure to drive their studies. I can see it working far better in the context of a masters degree, as you allude to.