It's just that often skins that have a void in the working area (pixels that are displayed on the game model) look very strange in the game itself. In principle, what you created is even more or less. It was possible to shape the character through shading. I agree that this is not as effective as the complete removal of pixels, but it looks nicer. Although, as my experience suggests, people really like skins of this type. I'm really very curious, people who download these skins, how long have you been using them?