I think the whole idea of sleep training has to do how much help the parents are getting during day and night while kids are young. My parents are from a traditional culture where grandparents would often live with the parents to help out day and night when kids are little, or in recent years, the family would contribute to hire a live in nanny to help out if the grandparents are unable to help. Sleep training is unheard of for my parents and people from their generation. They had so much help at home that they can afford to not have the kid sleep through the night until much older, 2 or 3 year old. Where as I live in a more individualistic society where having children and raising them are seen as a personal thing, no one is there to help if I am dead tired due to lack of sleep. Therefore, I sleep train. When my parents judge me for it, I just tell them that not everyone is as lucky as they were to get that much help.