There are several reasons why it has become a trend in today's society
The first reason is that grandparents have more time on their hands.
The second and most common reason is because of the relationship between mother-in-law and daughter-in-law, in most families the relationship between mother-in-law and daughter-in-law is not very harmonious, the mother-in-law is more nosy, and the daughter-in-law and do not want to be bound, so mother-in-law and daughter-in-law relationship is not harmonious, so the daughter-in-law can't believe that the mother-in-law and the father-in-law to bring.
Also in order to avoid and in-laws unpleasant, so that the husband in the middle of the difficult, so simply let their parents to help bring their own parents sometimes better understand their own daughters, the possibility of conflict will be very small, even if there is a contradiction, their parents will not be put in mind, after all, their own children. So in order to avoid unnecessary contradictions baby are brought by grandma and grandpa.
Thirdly, it may also be because the grandparents are overly spoiled, always feel that this is their own family flesh and blood, especially pampered, sometimes the parents discipline, grandparents are always not allowed. In order for the child to develop better habits so by the grandma and grandpa to bring.