Why does everyone talk about fearing God?
We do love God. He is our supreme benefactor, the most gracious and the most merciful. Piety in human beings is a manifestation of the love they have for God. Having fear of God is not in the same sense as having fear of a ferocious animal. Rather, fear of God is positive fear and can be understood in the context of obedience to God. While God is compassionate and benevolent toward human beings, He is also very just. Thus, fear of God is a result of the realization that God has the ability of punishing wrongdoers for their evil deeds. God is all knowing and nothing is, or can be, hidden from Him.
A person who has fear of God constantly lives with the sense of being accountable to Him. Even if his fellow human beings do not have the power to implicate him for his wrongful actions, a person who has fear of God knows that in the Hereafter he will surely be answerable to the Almighty for his actions, big or small. It is this that causes a believer to naturally fear God, a concept which serves as a source of reform in his life.
Source: The Seekers Guide