Because the only reason Sony is pulling these shows is because the license holder is demanding they do so. The license holder is WB. They are who Sony paid in order to provide you with a license to enjoy whatever media you bought. They are not reimbursing Sony to give you a refund.
This happens just about every single time a license holder pulls their stuff from any online service. It's happened with all the big names. Spotify, Apple, Google, Amazon, etc. there's always a major outcry about it but usually it's not the service itself but the license holder who is at fault. My view is we should start holding them accountable.
They can't agree to do a charge back unless you bought it really recently (within 120 days of purchase), and then only if you can prove you didn't receive the item in question which you did.