For as long as princess Lilian attended the Nobel award ceremonies, from 1976
Forhåndsvisning | Scanpix and forward until 2006,
Photo Gallery - The Nobel Prize Award Ceremony 2006 , she was seated in the front row. One reason for that was that there were only four members of the royal family who could be seated at the podium until 1995 when princess Victoria attended for the first time. When prince Daniel joined the royal family in 2010 there were six members of the family who could be seated on the podium, if all was to attend. There was no reason to move Lilian to the back row while she was attending the award ceremony, especially as Carl Philip didn't attend the ceremony until Madeleine began attending it.
It will be interesting to see how the seating arrangements will be next year when there will be seven with Chris (if he is to attend), it's possible that he and Madeleine will be seated in the front row the same way as princess Christina and her husband are now, and that the same will happen when Carl Philip marries, that he and his wife will be seated in the front row, and that only the king, queen, Victoria and Daniel will be on the podium.