Just because God is everywhere doesn’t mean that his presence can be equally felt in all contexts and all places. Some places, some states of mind, are closer to God than others. It gives us something to strive for, something to achieve.
God is transformative, if you get too close to him, you won’t be quite the same person after you leave his presence. He strips away parts of you that no longer are in alignment with your true self. Do this enough and you become God yourself.