For the same reason trees bloom in a disproportionately high quantity the spring before they die. When they sense the end of their lifetime they want to bear fruits. This isn't uncommon in people. The closer you get to the end the more you worry about your legacy.

What's more painful than death is not getting a chance to discharge at least some of your ideas. Ignoring your dreams is the number one regret of the dying. Death is not the worst thing that can happen to a man.