But I don't get why the refund is canceled and the coins just get destroyed. If you make a contract with a host and put money in and then put the host down just to get my own coins back I don't profit at all. What is the deal with it?
When a file contract is failed by the host, the renter recovers his allowance, and what is burnt is the collateral that the host put upfront. The renter can't have also the collateral as a "compensation", as it would encourage evil renters to make huge contracts and then DDoS his own hosts to make a profit from the collateral collected. For that reason, lost collateral is burnt.
What do you mean by without paying in SC. While the blockchain is working with SC you would need an direct exchange on the platform, isn't that right?
There are at least 2 projects I am aware(under construction) of services that will allow you to pay in BTC or PayPal and then upload your files. The services will do everything behind the scenes: buying Sia, making the contracts and so
This would mean a major step to gain acceptance. Do you have further links about this?