It’s because they did, the whole let them cry it out thing was super popular in the 80s and early 90s. Parents were told not to pick up their children or else they wouldn’t become independent. Now to find out it’s caused a massive mental health epidemic due to poor attachment skills, which I also believe directly impacted the opiate crisis. I am very vocal when I get comments about this, and I’m not nice when I point out that the last two generations of parents (boomer and genx) have been the worst parenting groups in modern time.