Why do high level players memorize specific games? Inspite of  having such a large number of possible positions and games why do  high level players bother about some specific game from some million years ago ? It may be helpful in understanding techniques and tactics but memorizing them seems very unusual. In fact memorizing games puts the person with more calculating ability at a disadvantage in time constrained games. Shouldn't the goal be to develop the chess aptitude rather than memorizing.
Memorization is mostly a side effect, not the end goal. Top players can spend hours or days analyzing a single game to try to understand all of the instructive ideas. Memorization naturally flows from that.