That is just because KE website is a crap. Also you should NOT purchase on KE website unless you're using Korean credit card because you have to visit KE office before your flight and show your credit card. It works well if you're leaving out of KE's direct destinations, though.

From BOS, KE codeshares with AS and you'll be able to get all KE-coded flights through SEA and ICN if you search on orbitz or elsewhere.