It is the host being forced to cancel. If you attempt to buy a sandwich and the sandwich shop burns down before you get your sandwich you don’t get a refund.
That is only because the sandwich shop has more important things to deal with, like the safety of their employees and customers. If you call up your credit card company and complain that you ordered a product that was never provided, you will absolutely get a refund.
So, SXSW was forced to shutdown? By whom? Did they lose the money that was paid them? How?
Even if they said, hey, we're trying to get X refund for Y site and facilities... we're expecting to be able to give refunds of Z% of your deposit amounts (expect at least 50-80%. I would think most reasonable businesses would accept that. A total forfeiture, someone is making money off of this and definitely not doing anything to earn it.