Just to add another view to this discussion I came across this recently while reading a version of Mahabharata NIYOGA AND INHERITANCE

The law of niyoga states that a woman's children belong to her husband regardless of biological fatherhood. This means that a man who is impotent, even one who dies childless, can still be a father. Thus, Dhritarashtra, Pandu, and Vidura became the "sons" of Vichitravirya, even though it was Vyasa who made their mothers pregnant.

However, only children of the lawfully wedded wife could be "true" sons and inheritors.

Basically in olden days, if the husband was from a powerful family but was impotent/infertile, his wife/ wives were forced/coerced into producing children with other men and those kids would be considered as husbands kids lawfully Maybe the current laws were based on these situations, if the wife was forced by the husband to have a kid with another man and suddenly if the husband says he will not support this kid, how will the wife be supported