Why does Neopets save card details when buying Neocash?

I use virtual disposable cards when shopping online. I just tried to buy neocash and the card declined because Neopets put through a HK$0 fee and attempted to save the card details, which is obviously not supported with one-use disposable cards.

Why do Neopets need to save card details for a one off purchase? I've heard Paypal is buggy, but I am not keen to have my card details stored by a company in another country who do not advertise that they do this, but I'm also not American and don't know if this is standard policy in America and therefore completely expected?