Well, you have some good points, but imagine if children can inherit good deeds of what their parents does, then the bad deeds should be for them too. The fact still remains that, they are blood. Which simply means the sin must still pass down to generations.
Imagine killing someone or spoiling someones life, there is nothing bad if the life of it's children too got spoiled. We all know the good and the bad, why doing something to hurt someone? Sometimes I don't pity people because of what they had done in the past.