In reality, users simply write down difficult passwords, leaving the system vulnerable. Security is better increased by designing for how people actually behave. By recognizing that the real goal of security is to minimize the relative amount of unauthorized use. Although a system with extremely poor usability would certainly discourage unauthorized users, it is likely to turn off the target users as well.
Random passwords are more secure.
A system-selected password is more secure than one the user chooses. Long passwords are more secure than short ones. Forcing the user to change passwords frequently increases security. Requiring different passwords for different systems increases security. All of these statements would be true if we did not have to consider the human factor.