Because it would make presidential election outcomes more likely to reflect the popular vote (which is the morally right thing to do), and because it reduces th

Because it would make presidential election outcomes more likely to reflect the popular vote (which is the morally right thing to do), and because it reduces the risk that small changes in big states create vastly different election outcomes (which is the strategically right thing to do, if you expect your opponent to cheat, lie, and start insurrections based on false claims).