Baby bunnies nurse only once or twice a day, They fill up with a huge belly of rich milk that sustains them till their next feeding. Rabbis do not stay with their young except for the 5 minutes it takes to feed. In nature a mother rabbit that stayed with her young would be exposing them to predators. So, the babies of mothers that milked fastest, with the richest milk survived to create babies of their own. Natural selection at its best.