Well, SK tries to be uniquely scandinavian. This is easy ex-ARN and CPH, but prohibitively expensive ex-NRT,ORD,BKK etc. So ex ORD you will get no reindeer, on NRT routes you need a japanese element etc. Hence different menus. ARN-ORD/EWR is the same as is CPH-ORD/EWR/IAD/SEA.

DL's move to serve everyone everywhere the same is silly. I often travel the same airline multiple times in a month and getting the same food on every route is lame.