Long answer:
Because SMF's next default theme is really what this should be made for.
The main issue here is that catbgs and titlebgs are all one image for IE and Opera compatibility purposes, and unless I go through and change ALL the code for catbgs and titlebgs, or do some kind of hacky javascript fix (which I'm not doing), the images have to have every component for the catbg and titlebg.
In more practical terms, that means that while the category and title backgrounds display fine on the Board Index, they cut off on the other pages. I can overcome this in Firefox and Google Chrome/Safari by using a CSS property that is specific to those browsers (actually their engines).
But in short, to fix this would require a recode of all pages, and this would be pointless since SMF's next default theme already does this and includes the necessary code. So we'll all have to just wait for it to be released until I can actually "fix" this theme.
And as far as converting it to 1.1.x, it would be even more work to change the coding and so forth when SMF's next New Default Theme comes out. So really, this is something that can be achieved, optimally on a theme based on Curve, and not Core. And SMF's new default theme will be for SMF 2.0 only. So that further negates the benefit of theming this for SMF 1.1.x, since it still won't be "fixed" for 1.1.x.
If you or someone else wishes to convert this theme to SMF 1.1.x for personal use, that's fine. Just leave the credits to me and Bikken/Dziner there.
If someone wants to convert this theme to SMF 1.1.x and redistribute it or share their changes, then they'll need to contact me for permission first.