Butterfly effect?
Indeed there are events of catastrophe results that are caused by an person action/decision. But not everyone in the world, world in your sense, have the capabilities to do that. Most of the people in this world are sheeps and do what are taught/told to them. They might rebel a little here and there but they are still sheeps. Their overall actions have little consequences to the world you speak of. We might affect the life of the ones we have close contacts with but the inaction or action of regular people have little to no effect of the "overall world".
Case and point, media propaganda on human actions like school shootings, Asia planes crushing, terrorism.
The first time around, everyone in the world is sad, emotionally affected and pray for the safety of the victims. The second time around most will repeat what they did previously. Third time around, nah. Fourth nah. 56th time nah. The only impact these events have are on the family members of the victims. When it happen more than enough time, it would just be a newspaper and small chat for 99% of the rest of the population, nothing more.
And THESE are major events, sort of. If they have little effect on the overall world couple months/years down the road, what makes you think the action of an individual make a difference?
I'm not saying we can't affect lives. Hell, it would be impressive if you can help 20+ individuals throughout your entire life, and I mean help in the sense that actually deeply changes them and the way they live. But these 20 individuals doesn't necessary pay-it-forward and affect the ones around them. It just stops eventually.
Ripple effects stops eventually even though we are taught otherwise. This is physically proven by throwing a stone in the river near your house and the ripple wouldn't even expands more than 10m much less reach the lake in the next state. It's all an idea sold to us from education, media to make us "a better person".