Why no gtkbutton cell renderer?

[Paul Stuart <Paul_Stuart seektech com>]

Hi There,
 I was surprised to find that there is no gtkcellrenderer implementation for a gtkbutton. I understand that one can create a custom cell renderer, but is there a reason why this isn't part of the vanilla set of cell renderers? Seems like a useful widget to have.

Just curious/hopeful someone can point me to their gtkcellrendererbutton.c code :)
Paul