They're actually not. There are lots of women who want to breastfeed but can't physically do it. Via medications or health reasons, lots of moms can't produce enough milk or any at all to sustain a child's needs.
Another issue is her eating the bare minimum, if her claims and the pics she posts of what she eats are accurate and she's breastfeeding, she's a moron. Her body is being depleted. Eating an extra 500 calories a day when breast feeding is standard. This girl looks like she eats 500 calories a day... in general.