I don't think you fully understand what these "color tables" are. They are ICC profiles, and they have a purpose. They do not degrade colors. They enable your browser (if it is a modern browser) to display color accurately.
In the example in the article, the embedded profile does nothing at all, because the default for the web is already sRGB. If your image, on the other hand, is in some other color space, such as Adobe98, the embedded profile allow the image to be displayed correctly in modern broswers. Without that profile, the colors will be wrong. Of course, in older browsers, the colors will be wrong regardless of the embedded profile, because most older browsers do not support color management. That is why, for display on the web, images should already be converted to sRGB. Most photo sites do this automatically.
1) For small images, the table is bigger than the raw image itself, as this article amply demonstrated.
2) For poor quality images, colour quantisation does not save anything.
3) Good quality images with subtle colours are degraded by it.