The Holy Spirit used my sin to convict me of my NEED for God. Then I accepted Christ. That's a pretty good reason. :) I love God much more NOW because I know of my sin and how it alienates me from Him. Because of my sin, I appreciate His love for me a hundred times more than I would have, had I been protected from all sin. This is one of the main reasons I think it disrespects Mary to say she was sinless. Catholicism denies her what we sinners know all too well, we NEED God.I fervently agree that what took me to "the next level" with Jesus was my own desperate awareness that I was "fell full foul in sinne" and couldn't bootstrap my way out of it. So clearly in our own lives we experience the truth that for the God who can turn the murder by torture of the only righteous man who ever lived into the salvation of the world turning our sinfulness to good purpose is no challenge.
But I want to maintain that it is not necessary for a human to sin to know how much we need God or to love Him. As Lewis says, it is waking that understands sleeping, not sleeping that understands waking. In my somnolent stupor, like a man who has heard the alarm and struggles to make himself get out of bed, my sullen, groggy heart blunders to-God-ward. But I suspect someone who was never drugged by sin would all the more lithely and eagerly give all his (or especially her) heart and attention to God. It was not so much sin itself, but the gracious awareness of the horror and sickness of sin that God used to bring me to Him. But rescue from moral and spiritual death is not the only thing that makes Him lovely, and the eyes of the sinless may see those beauties more clearly than we do, at least than we do now.
I suppose it's the old "knowledge of vs. experience of" question that can be argued reasonably on both sides.