There are artistic reasons why you would want to indicate white as the skin color. For example maybe you want a snow woman that fades into the snow.
Which... Is the whole point of using AI. To be able to generate lots of different pictures based on your prompt.
That's perfectly reasonable.
Or maybe they just wanted a picture that looks like themself to post as a profile picture, for example.
Id hope that you don't support people posting profile pictures of themselves in blackface.
And in order to not do that, the AI needs to follow the prompt of the user.