Isaac was the type of person who followed his father Abraham in nearly everything. This was the way Isaac was. Isaac copied his father in all things, even his sins, like passing his wife off as his sister in Gerar. Isaac followed in his father s footsteps in everything, and I think also in the tithe. Jacob therefore learned about the tithe from his grandfather and probably also his father.
Stewardship runs in families.
Children learn about God, worship of God and service of God and giving to God from their parents and grandparents. Stewardship needs to be taught in the family - by example and by word. This is true of everything concerning our faith. Faith in God runs in families and so does stewardship. You learn how to give faithfully to God from your family.