A lot of it has to do with the budget. There's only so much money to go around. That's why most of the other staff are unseen and/or unheard. We've seen the hall boys, several of the other maids and we've heard the "outside staff" referred to but none of them has said a word. They get paid more if they speak.

FWIW, Daisy is not at the bottom of the kitchen staff. She is the Assistant Cook. Ivy is below her although I'm not sure what her exact title is or if there is anyone below her on the kitchen staff.