Why is it also that it is thought of as "selfish" to worry about your beauty when the benefits to a child are not truly established?
Today most folks appreciate that adults make choices about their lives. If a woman chooses not to breastfeed, I wager that, while there may be some who consider her "selfish", the vast majority will not, and will rather simply acknowledge without judgement that a choice was made.
As for the benefits of breastfeeding, these are indeed truly established by countless medical studies.
A personal recount. My first child was breastfed for two weeks, but my wife could not continue as her nipples became cracked and very sore, and so my first child was bottlefed thereafter. For the second child, my wife prepared her breasts by periodically rubbing them with a towel to toughen her nipples. The second child was successfully breastfed for eight months. My first child has Type I diabetes, a very serious disease which research teams of the Children's Hospital in Toronto have linked to bottle formula containing cow's milk. This is not to say all such circumstances give rise to Type I diabetes, but this does state that there is a greater risk, particularly if coupled with any degree of genetic disposition. Only as a matter of fact, without any speculation, my second child does not suffer from diabetes.
While it is obvious to even the most dim-witted that women's physiology appears hard-wired for breastfeeding, in addition there are a mind-numbing number of medical studies out there on the topic. Virtually all of these support the health benefits of breastfeeding infants, with the obvious exceptions of where the mother's life patterns inject harmful substances into her breast milk.
Just to mention one medical study, it cites the presence of "
hard evidence indicating that long chain polyunsaturated fatty acids (LCPUFA) naturally occurring in breast milk may play a significant role in babies’ brain development. Until recently these fatty acids were absent from formula milk as it was assumed that babies could synthesise their own." Again, this does not mean that bottlefed folks like me, who consumed formula prior to the addition of fatty acids, are dummies, but this does point out that nature seems to have a significant purpose in the act of breastfeeding. And, generally speaking, one can also wonder about synthesized additives in any part of the food chain.
As for the psychological benefits, these are de facto less hard science due to the necessarily subjective nature of the adult participants in any test sample. But even a fairly skeptical person, if applying a modest degree of common sense, would acknowledge at least the potential for such benefits for both the mother and the infant - later life challenges notwithstanding.