If one has balls, then one is a man, and it is being a man that makes one capable of [insert AWESOME THING here]. If one does not have balls, then one is a woman, and as we all know, a woman is inherently inferior to a man. Having balls isn't about being tough, it's about being a real man, and real men do whatever the hell they want, whenever the hell they want. Like include nipples in computer games. If a man refuses or is incapable of doing [AWESOME THINGS], then one is not a real man, which makes one inferior. Like a woman. Hence, "no balls".