Only an immigrant knows the that the context and time period of these archaic symbolism. The sixth guru in 1969 mandated the knife as part of the 5 symbols of faith. 

As a self defense and to protect others . But that is in India, a different society and environment. If as a sikh you want to prove your faith I am sure your scripture has more spiritual sayings, rather than observe a universally  uncomfortable symbolism.

I strongly suspect that it is a personal belief or simple ego or simply the clamour and glamour of school children like wearing the latest reebok shoe. Just to define your identity to your own ego.