The point is power
Organization has one purpose: to exercise collective power. For individuals, in all but the most rare and exceptional circumstances, the most effective way to assert and magnify power is by uniting with others to act. Collectively, people are able to assert power much greater than the sum of their individual efforts, and the more highly organized a section of people is, the more power they are able to exert.
For example, at present, a relatively small section of people is setting the terms for all the rest of us, and we submit to their will. They are able to do it because they’re highly organized. They can wage war to conquer nations. They can impose and run a global economy. They can extract natural resources at extreme volume and speed, coerce others to work for them, and manufacture complex items like spy drones, bullet trains and synthetic drugs. As individuals, we can’t do any of those things. Nor can we, as individuals, stop others from doing these things.