There is a huge difference between the consort of the sovereign and his sisters. Itís natural there is different expectations and levels of criticism.
Look at the siblings of any reigning monarch? Do people blink if Carl Gustaf sisters donít attend say the Nobels? No. But if Silvia didnít??? There would be shock and definite questions. Same with any monarch. No one blinks if Felipes sisters are missing from a bigger event but Letizia is another matter.
Caroline is no longer the First Lady of Monaco and Stephanie never was. They both attend events are involved in Monaco. But they have a balance.
As for their families many live and work outside Monaco and have their own responsibilities to see to.