Actually Ber, you bring up a very valid point.
Why does Drupal ship with drupal.css and etc? Isn't that just a file for themers to use? Why should they have to write overrides to get that crud out if they don't want it? Shouldn't it be the other way around, write a file to include it if they so desire?
Simple: because Drupal is not JUST a development framework. It is, out of box, a functional web site CMS. A lot of stuff that we take for granted (having an 'edit' tab when we have perms to change a node, for example) are handled by that CSS file. Obviously, there's a case of creep somewhere along the line as unecessary CSS code snuck in that goes way beyond those basics. All the styles for drawing archive.module's calendar, for example, would best be moved into archive.css and included as needed IMO. Come to think of it, that's a nice idea for a patch. But, to return to the question, eliminating all CSS from core would be a definite mistake IMO. Stripping down drupal.css to a bare minimum, though? I'm all for that. --Jeff