The fact so many women do vomit during labour actually illustrates the importance of keeping good to a minimum (and light snacks which will be more quickly broken down than fatty or high protein meals), and in some women avoiding food entirely. When you vomit normally it ends up on the floor or in a bowl, but if that stuff is all sitting in your stomach and you need a general anaesthetic for a crash c-section it will most likely spill up into your throat and most importantly, because when anaesthetists you loose your protective reflexes, it will then go back down into your chest. This causes an inflammatory effect in the lungs and the woman can end up in ICU on a ventilator or even dead. It also delays the time to getting the baby out so the baby's life is at risk also.
I think we need to be sensible about these things (and a lack of nutrition in labour isn't good either), and don't believe in fasting EVERYONE, but it is justified in women who are Hugh risk. Also, i'm afraid going into labour with a breech baby is most definitely in that category and I think it would actually be negligent for a midwife to encourage you to eat in labour if your baby is breech as the risk of c-section is so high.