As an almost 59 year old mother who is still quite sexual, I certainly don't think or feel that way - but a lot of America does. It's a pretty pervasive sociological phenomenon. When Kim K showed her ass on the cover of that magazine, a lot of other women her age scolded her for doing so because she was "now a mother."
Elvis Presley rather infamously couldn't have sex with a women who had given birth - which kind of killed his marriage. He was certainly not the first nor the last man to feel that way.
Sex researchers note this as a common issue, that the role of wife and mother is often viewed as "caretaker, and nurturer" and not as sexual human being. I don't think that's about capitalism, I think it's about patriarchy.
Though countless articles encourage women to get in touch with their sexuality and bounce back post-baby, the reality is that if a mother openly embraces her sexuality, she is perceived as being someone of loose morals, and even worse, not a good mother. The message? Motherhood and sexuality cannot coexist.
https://www.scarymommy.com/can-motherhood-and-sexuality-coexist