What is the point of humans training to become stronger? when we could be killed by any weakling with a weapon?

seriously, whats the point. I've done kick boxing for 4 years, and boxing for a further 2, life weights 3 times a week, and feel quite strong, however, I still feel powerless. If i was to get on the bus and somebody put a blade to my throat and asked for my phone, money etc..., really what could i do to stop them. If some pyscho pulled a gun out on me, no matter how stong the guy is, he is always going to win once he pulls out a gun. I find it really frustrating that no matter how hard i train, I will never be truly strong because everyone carries a weapons