Why do they not paint a line about half way up the Fenway Park Green Monster wall so a HR counts if the ball hits above line?
Because you would ruin the stigma, of what makes Fenway one of
the best parks in major league baseball. In other words, without
the Green Monster, and what it does, Fenway would be just another
ball park. If they did that ... then one of those bloop hits that
just scrapes the wall and results in a double would be ruled a home
run. I will grant you that a line drive that hits high on the wall
would be a home run in another park, but the risk of awarding home
runs to weakly hit balls that wouldn't be a home run in any park
outweighs the loss of those hard-hit balls that end up only being
singles or doubles.