Breast isn't actually Best.
Mammals make milk. It’s actually why they are called “mammals”. It is made by mammary glands, which we also call breasts. From elephants and blue whales to mountain pygmy possums and fruit bats. The females of all mammalian species give birth and make milk.
mammal
/ˈmam(ə)l/
noun
a warm-blooded vertebrate animal of a class that is distinguished by the possession of hair or fur, females that secrete milk for the nourishment of the young, and (typically) the birth of live young.
Humans are mammals. And we make milk. Always have, always will. Like all the others, human milk is species-specific.
There should be no reason to promote breastfeeding, let alone list the “benefits” of human milk for human babies. But millions of dollars are spent every year by multinational brands whose profits rely on parents choosing their version of breastmilk substitutes. The packaging of these products is where you will find the statement “breast is best” - followed by the word But.
Targetted marketing begins during pregnancy, assuring parents that only the best will do. The language is carefully chosen to make sure parents feel good about intending to breastfeed but - most importantly - be assured that the next best option is their product. Unfortunately, there is no requirement for brands to inform parents of the potential health risks of replacing human milk with a manufactured alternative.
The reality is there is no comparison between human milk and infant formula. Parents aren't shopping for a car or washing machine! Very few mothers start their babies on formula from the first feed. Most intend to breastfeed.
If breastfeeding doesn't work out, there are products available to feed babies. There isn't much difference between different brands and the end price is mostly covering the expense of transport, advertising and profits for shareholders. A fairer system would be a heavily-regulated industry prohibited from advertising and a basic product made available to those who need it at cost.
Breast isn't best, it's just part of life.