Sometimes we look at the past through rose-colored glasses, and everything seems very idyllic. But, actually a hundred-years ago, factories were in full swing, and people were rapidly shifting from traditional ways of doing things to more modern ways that often utilized commercially-produced products. Sometimes this was good; other times it may not have been. For example, in the early twentieth century, a rapid shift was occurring in how infants were fed.
Breastfeeding was in decline, and was viewed as something done by women in the lower socio-economic classes.
The real decline of wet nursing came, of course, with the rise of formula bottle-feeding, which began in the 1910s. Bottle feeding was convenient (especially for women busy outside the home); it was “scientific”; and it was “modern” – it was what mothers who were “with it” did. From that point of view, only primitive or unenlightened women breastfed.
Source: Breastfeeding History (Made in America: A History of American Culture and Character)
A hundred years ago, magazines contained advertisements for baby bottles that made mothers feel good about bottle feeding. An advertisement for the Hygeia Open-Mouthed Nursing Bottle emphasized how much babies liked the nipple design and how easy it was to clean.
In comparison, today new mothers are encouraged to feed their babies breast milk. It is generally considered superior to formula (and high-quality breast pumps are now available that can make it more convenient to pump and store milk). According to the Centers for Disease Control and Prevention (CDC), 82.3% of the babies born in the U.S. in 2015 started out breastfeeding. At six months, 57.6% of babies were still breastfeeding, though only about 25% were breastfeeding exclusively.