Not forgotten, just not included because:

It is only an in-ground value with extraction, processing, royalties, taxes, management, politics and what have you, not factored in.
It is meant to compare one company to another and all the above factors vary from company to company hence when making comparisons it is best to filter out as many of the variables as possible.

It does not imply an actual value of a share price but I used it to emphasize the ridiculousness of some valuations and recommendations of bank type brokerages, and how Nevsun is being undervalued.
Cheers.