At least in my case, sample size: 6, we socialize with other parents of babies of a similar age. 2 other couples did sleep training and reported similarly good

At least in my case, sample size: 6, we socialize with other parents of babies of a similar age. 2 other couples did sleep training and reported similarly good results, 3 other couples did not and report terrible sleeping habits. It costs nothing and takes a couple of weeks to implement, and the whole family reaps the benefits. Do you have an argument against sleep training?