The problem with StyleXP....which is clear and apparent to WB skinners in particular is that it is limiting in creative freedom.
For example....I have my buttons on the left....primarily because I can, but also because it is suitably different from the default placement to actually be 'creative'...da-daaaaa!!!
Sure, a graphically competent StyleXP skinner can create a pretty, even 'perfect' rendition of a predictable skin.....but those who actually want to be different have to look beyond the limitations of something that is little more than a default skin re-bitmapped.
Users 'may' not understand or 'see' the difference inherent within the two formats....but those looking for added functionality of the GUI interface have no option but to choose WB over the dll hack.
In exactly the same way that alternate shell users and Explorer GUI modifiers such as Object Desktop seek an escape from the default Windows look and interface, so do Window skinners seek diversity and freedom of design.
Re-hashing the default is like a photoskin of WinAMP....too damn easy and just plain fugly...