Asiana Club - Booking cities connected through ICN

I've tried (just for pricing reasons) booking a flight from SEA via ICN to another city (SIN or HKG as two examples) and their system doesn't seem to allow it. Nor can any other major site (Orbitz, expedia, etc...) seem to do it either. The flights simply don't show even though I can book them separately. Doesn't Asiana allow (or contemplate) anyone using Inchon as a hub or am I missing something? Using it as a hub w/o being able to check bags through and being able to get boarding passes for the whole trip would be a definite negative.

Well, I tried and succeeded for SEA-HKG booking while couldn't do to SIN. I found that if there're no seats available, they don't show any. Try other date or call them. Or use local travel agency - usually better options are available on agencies for Asiana case.

I think its because of the flight timing. From SIN, its a red-eye flight. You arrive at about 7. Then the North America departure bank is at 4-6pm. I think OZ knows that its too long a wait and does not even bother to show it. However, I have been able to book, but only the SQ codeshare from SIN-ICN shows up.