The deity is handing control of the afterlife and immortality or reincarnation to a mortal. The ankh is a symbol.
Your life is the stem. The cross piece is the divide, the loop is the afterlife path and in other depictions, the afterlife is held and controlled by the deities. This is a handing over of a sacred power.
Something doesn't want mankind to know this power has been given long ago.
There is one way now. Notice how the symbol only has one way. The doesn't need to be repetitive reincarnations back into the physical any longer. No greater gift.