Breastfeeding vs formula! Help!!

Ta

My 11 month old baby has been breastfed since day 1, but her pediatrician wants me to start giving formula to her when she’s 1 year old. I’m confused because as far as I know, formula should only be introduced when the mother is unable to breastfeed or when the baby isn’t gaining enough weight. None of these is our case! My baby is healthy, she’s gaining weight normally and my milk supply is ok! I don’t know what to do!! 😭