14 month old & nightime feedings?

Hey ladies, my daughter is 14 months old and her doctor told me to cut down her formula to 16 ounces a day so she’ll hopefully eat more table foods. So here’s my question, she goes to bed with a bottle (6ounces) and she’ll finish it. She usually wakes up during twice and I give her another 6ounce bottle each time and she will finish it and go right back to sleep. Why is she so hungry during the night? I’ve heard the most kids can sleep through the night by now?