Answer:
I'm not so sure that Polonius was such a good father. He relates to his two children, Laertes and Ophelia, the same way he does with everyone else: he doesn't do a lot of thinking, is not very deep but is stubbornly opinionated, and he talks far more than he listens.
Everyone knows that Polonius is a doddering, garrulous, self-aggrandizing old fool. Just the kind of advisor a snake like Claudius would want: someone who is weak minded and easily used and manipulated. If he were a different kind of person to his children, fine, but he isn't.
When we see him with Laertes, who is about to go back to school, he gives Laertes a long, obvious, cliche-filled speech, replete with maxims that the learned Laertes must have heard a hundred times before. As he pontificates, Laertes listens dutifully, for he has already learned there would be no use in talking anyway. It's not that Polonius doesn't care for Laertes; it's just that he's all surface and no depth.