Because in these cases these people have gone so far as to hire lawyers to send notices to Google about the problem and nothing gets done. Imagine everytime someone google your name - potential employer maybe - and it came up with a bunch of links about you being a gangster or child rapist or the like. What if these links are in countries where you have no legal recourse or the cost of getting them removed is too high? No, Google has a responsibility here. Everyone is accountable, there is no 'I was just following orders' bullshit.
"We choose the right to be who we are. We know the difference between the reality of freedom and the illusion of freedom."