That would usually be like several hundred / few thousand known issues per game. Would you buy a game that has about 3,500 open bugs?
Would you buy any software product knowing the amount of issues they have in their issues database?
EDIT: Just to give a very simple example: Firefox.
The address bar, the download window and the bookmarks and history panel in Firefox, combined, currently have 1,415 open issues. Just those 3 parts of the browser. Now imagine how much there is in total, and how much there would be in a very large video game, something massive and open world like World of Warcraft or Assassin's Creed or something similar.