Copper areas are used to define the boundary for Pour Copper to work in, but we recommend that they are not deleted after Pouring.
Once the copper has been poured, it is tempting to remove the copper area from the design. However, it is best to leave it there, as it is useful if you need to re-pour the copper later on, perhaps after modifying your tracks following a design change. Areas are not included on plots anyway, so they won't come out on your artworks. If you don't want to see them on the screen either, simply use the [Display] dialog to set Areas as invisible.
If a copper area is poured, and the area is then removed, it would then not be possible to re-pour the copper after any modifications to the design. Although an individual copper shape can be poured, this will only pour within the boundaries of that one copper shape, not the whole area that was originally poured.