It's not losses regarding damage, or the client cancelling. The host cancelled, services not rendered and the transaction is therefor incomplete.
If I buy a sandwich from you and you take my money, the transaction isn't complete until you give me the sandwich ordered, regardless of your refund policy.
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.
A couple of reasons:
1) Their "policy" does not override consumer protection laws.
2) Even if it was enforceable, when enough people call their credit card companies and request refunds it will cause so many problems for them that their "policy" will change.
If you pay for services or goods you should expect to be rendered those services or gifts in a reasonable time and manner. There are consumer protection laws that state exactly this.
The seller purported to be selling a service/product that was not provided.
In the US, the terms of service, policy, EULA, whatever, carries very, very little weight compared to the fraud committed by the seller. If you sell someone a thing, you provide them the thing, or the buyer chargebacks.
If I buy a sandwich from you and you take my money, the transaction isn't complete until you give me the sandwich ordered, regardless of your refund policy.