The stains are still there, but they're just a different colour, it's like people turning their hair white with peroxide bleaches, or making a limed-up toilet bowl look "clean" by bleaching the lime white, and even with that Retr0bright formula, you use oxy-bleach to bleach the yellowness out of plastics so, it's more of a mask than anything, it's just that people are so used to using it as a cleaner that they won't use anything else...
I wouldn't use bleach in anything but the washing machine (to clean it out if it goes a bit smelly) or in the bucket of water to wash the floors myself...