Why? This would keep the software and the interface simple and more consistent. Look at the links to namespaces at the bottom of pages. Sometimes there is none, sometimes one, sometimes two. Why is that? And why on earth is the link to a discussion page called a namespace? And why is there no Talk page for SpecialPages?
I think constancy is not the solution, it's the problem.
The special namespaces contain pages which are functionally different from standard wikipedia pages. Talk namespaces are for discussion of articles, and user namespaces are for interaction with other wikipedians. These are NOT encyclopedia articles, and I think it behooves us to help anybody who comes to wikipedia to gain a clear and distinct understanding of this point as quickly as possible.
I would actually suggest that we try somehow to change the "look and feel" of the special namespaces, so that people will just SEE the distinction as they browse through our site. The fundamental problem I have with using () both to disambiguate terms within the wikipedia, and to denote special pages which are not encyclopedia articles, is that we don't want people to accidentally miss this distinction and start using the standard encyclopedia article namespace for user pages, or for talking about articles, etc.
Making the distinction as clear as possible is and important goal -- in my opinion more important than simplifying the way namespaces are handled in the code.
That said, I think we can and should look at ways to make the current interface more self explanatory, so that the links help users make the necessary distinction between wikipedia and the necessary wikipedia related pages.
Yours Mark