I love my GNOME developer friends but I do actually firmly believe this. Theming is accessibility, and any desktop environment not embracing it is shooting itself in the foot (heh). It is impossible to accommodate every user's colour, iconography, etc. needs, and that's where theming comes in.
I would not be able to use GNOME without being able to change its icon set. I am thankful that hasn't been removed yet, but I wouldn't be surprised if they'd like to.
