Agreed to the fact that we are not sure what actually was the scenario during Guru Nanak's time.. What ever we know is from and history can be wrong..
Regarding Bani, Seva, and Simran, these have effect on ourselves as well as others so are completely different from the 5 K's. 5 K's *might* have psychological effect on some. They might be a source of inspiration for these people but not for everyone.
Bani, shows the path we should follow in order to achieve happiness and for leading a truthful life. Seva, helps in eliminating ego, bring equality and an urge to help others. Simran, helps in freeing the mind from the worldly troubles thus controlling the social and mental problems like stress. Unfortunately, I don't see any such good ppint in maintaing the 5 K's.

Regards,
jodhbir.