Because they don't care if you actually get the seeds. It was illegal for you to order them in the first place, so you can't get pissed off at the seed bank. It's part of the territory. Your seeds get seized, just order some more from a different company and move on.
It's like getting busted with weed in CA. They take it away and write your ass a ticket. It hurts to lose it, but you were breaking the law and should be ready to accept the consequences without complaining.