We need God to be a Father to us—for our most basic conceptions about God, relationships, moral teaching, skills for living day to day, ability to relate to people in intimate ways, confidence to step out and take risks are all conditioned by our experiences with our parents and family and then sometimes with friends. Also, any honest assessment leads one to conclude that, to one degree or another, we are all wrong in how we see God, ourselves and others. Some of this error comes directly from the negative role that others have had in shaping our views of reality.
Thus the first and most obvious reason for us to know God as Father is because we need to have our erroneous ideas corrected. And who better to correct and clarify what life is really about than the One who created it in the first place? Jesus said plainly that he had been sent to introduce us to the living God. Since we believe (at least in theory) that he is right and that he came to free us from all forms of bondage we should do as he says. To know God as your Father is to know freedom as a human being.
Need more reasons? Do you think that Jesus ever lived in bondage to anything? “As it is with Jesus so also for his disciples”: Just as Jesus came to share in all things human—except to choose to sin himself—so too is all that he knew and did in relationship with the Father to be ours. He knew God as his Father and he was the most perfect and free human being to ever walk on the earth. To learn to trust and obey God is to know freedom as a human being.