Well, you have kind of answered your own question here. Yes, most CAD programs do offer the ability to work with an inverted canvas because most CAD programs worth considering that were developed primarily for the desktop market typically have some degree of AutoCAD compatibility, albeit with, more often than not, a substantially better user interface. Older CAD packages , such as MicroStation, also have this functionality because they have the same dedicated workstation roots as AutoCAD.
As I stated earlier, CAD work is not typically color-critical and WYSIWYG is important only in that what you draw is what should print, color notwithstanding. For other types of graphic design, color ranges from important to critical and the color of the canvas does affect the appearance of the content. A colorful diagram does not have the same aesthetic on a black background as it does on a white background. So unless the final design is intended to be displayed on a dark background, designing it on a black canvas would be a poor design practice.
The GUI protocol uses a white background because it represents the medium upon which most illustration and imaging is created: plain white paper. The same goes for other software that generally represents a real-world activity—e.g. word processing, spreadsheets, etc. The whole point of a graphical user interface is to be a virtual representation of a real-world workspace and people do not commonly work with black paper.
If your display is hurting your eyes, then it seems that the real problem may be that you need to calibrate your display or dump the Dell UltraSharp ;). (Dell’s displays are notorious for being too bright for serious design work even after being calibrated.) A properly calibrated display should cause no more eye strain than looking at real paper all day. I have a 30-inch Cinema Display that lights up my room if I were to turn off all ambient lighting after sunset, the 22-inch Cinema Display did much the same, and it does not hurt my eyes even after working for upwards of 10 to 12 hours on various projects. And trust me, my current beast is substantially brighter than what it replaced which was pretty bright itself.