Because she's the love-interest role with the will they won't they situation with Kate. And she may not be GCPD, but the Crows aren't too far off it in that they are legal while vigilantism is not. But fine, 'stand-in', if you prefer.
Point being, since the Arrowverse tends to do it's own thing, unless they are able to bring Renee in later on, the possibility is still there that Sophie could become the Question. They changed Bette into Mary, and made her a step-sister instead of cousin, so there's no reason they couldn't give Sophie some Renee storylines.
Not saying I necessarily want that to happen, or not, just that it's possibly what they might do.