I mean, to be fair, this isn't an uncommon story cliche.
He's Geppetto. A lonely man without a wife who wants a family of their own. Its the same premise as why Dr. Light built 2 robot children as his first creations.
He wasn't trying to create Super beings anyways, he was just trying to create a family.
Now, a logical person would just have adopted, but lets ignore that.
A logical person would also just get married since he looks fairly decent looking and looks young, but its canon that the professor has HORRIFIC luck with women.
