Now, suppose you have created a mock website using the graphical interface of Inkscape and you have handed off all of your files to the programming team. Suddenly, your client decides that they want all heading text to be a specific color of gray (4d4d4d).
Do you have to open each graphic file and make this change? Maybe. But you can also change it right in the XML Editor (and if your programmers are using your SVG files directly, they might even be able to make the change).