Re: [css2.1] :first-line behvior

At 19:16 19/03/2008, David Hyatt wrote:
>http://www.w3.org/TR/CSS21/selector.html#pseudo-elements
>
>"Pseudo-classes are allowed anywhere in selectors while pseudo- 
>elements may only be appended after the last simple selector of the
>selector."

I've seen this before, and often wondered: why?