Why do you think the goal of world peace has yet to be achieved

Because there are people who still think that violence is an answer.

Simply put, those in power don't want peace. Greed, selfishness, ignorance, hate, classism, racism, and twisted ideologies are entirely too common. We aren't working together, so many of us lack empathy. Greed drives pretty much everything mentioned in the second sentence. The pursuit and maintenance of wealth is why so many have a government that works to keep us divided and fighting amongst ourselves. It's why education has been dumbed down and higher education is costlier to pursue. Of course, they'll never admit that because they rarely ever take responsibility for any of their underhanded actions, which is another glaring flaw of those in power. They know that an ignorant populace is an easily controlled populace. If those in power wanted peace, they would work toward widespread enlightenment... But they don't, which should tell you more about them than anything that falls out of their mouths on the campaign trails.