What other reason must there be, other than our human responsibility for all other humans - our moral responsibility to be kind and compassionate towards everyone?
Children did not ask to be brought into this world, but so what? What prevents that argument from extending to all ethical responsibilities: "I did not ask to live, so why should I refrain from randomly beating people up if I feel like it?" One might respond, "because randomly beating people up is harmful" and that is true - but it is also true that neglecting to care for someone is harmful.
A good parent does equip a child with the necessary tools to go out into the world. But one of those tools should be compassion for everyone, including the parents. Besides, if the parent did a reasonably decent job at equipping their child for adult life, shouldn't the child appreciate this love and effort by reciprocating that love and effort?
It is commendable that you have have taken steps to insure that your children will not have
to take care of you, that is good parenting. But why should this preclude them from caring for you? I do not know your age, but I do know a number of elderly members of my own family - I have noticed that as they advance in age, as friends pass away, and as spouses pass away, that these elderly people becoming increasingly lonely and there is no better cure than the loving attentiveness of children and family.
It seems quite natural and proper to me that a good child should desire more than revisiting memories of parents; it seems natural and proper that they should desire to do whatever they can for their parents, even if it as simple as taking them to a movie, or dinner, ect when they can.
Or maybe I just read the Analects
one too many times, but I am fond of filial piety to a great extent (though I do have some objections):
Filial piety - Wikipedia, the free encyclopedia