[jsprogrammer]

Or, just allow the element to be styled like every other thing on the page. Because...why not again? Imaginary 4th wall that the bar is the only thing on the page that should not be stylable? So that it can match the scroll bars of native applications?

[radley]

You think users want the browser window scroll to change color / shape / width per web page? Wouldn't that get confusing?

[jsprogrammer]

You think users want their browser text to change color / shape / width per web page?

Page scroll is not the only place scrollbars are useful. If you have an overflowing div in the middle of the page, a fat white/grey scrollbar is confusing.