Why is personal responsibility so vital to freedom?
Freedom requires personal responsibility because freedom requires virtue. Personal responsibility is a human virtue. It means that we must strive for personal growth that only comes through the exercise of agency in making day-to-day decisions leading to human betterment. Personal responsibility also requires us to recognize how our own lives fit into the world around us.
Practically speaking, a free society cannot long afford personal irresponsibility. It cannot sustain people who live off the sweat of the brow of others. Not only do such poor choices stunt personal growth, they bankrupt nations financially and civilizations morally. We honor our free society by doing all we can to be self-reliant and live providently, both of which require us to assume personal responsibility for our actions and their consequences.