Well, there were stories of unburned bodies found floating in the rivers, there are many who couldn't afford the cremation. There's the official rule (registration needed) and the reality on the ground: insufficient government service coverage leading to undocumented births and deaths.

Even China has a lot of undocumented births, because of the 1-child-policy: https://thediplomat.com/2015/03/chinas-hidden-children/ (IMO the accepted "legend" that there were a lot of abortions just demonized the Chinese, whether nefariously or on purpose)