People would lose interest after the 11th or 12th inning, and start emptying out of the stadium and switching the channel. Plus would kill the pitchers. Some will disagree, but the ghost runner has to do with improving the product for the average fan, and possibly to reduce the risk of player injury, particularly pitchers.
With the rule changes I'd like to see the ghost runner at 1B, and bring steals, hit and run, bunts (!?*) more into play