One of the reasons to not cut your hair and wear a turban is that a Sikh can't hide out in a crowd. You always know who is Sikh. This coupled with the mandate that a Sikh must always help those in need means that you always know where to look and ask for help.
From my perspective (US), this is a much needed belief today since it was born out of the similar circumstances in 1699.
You’ve come across many good Shik’s? I wonder if you told them to their face your viewpoints on their irrational beliefs, somehow I doubt it and that’s why you edited your comment from “irrational beliefs” to “out of context”.
I felt irrational was too strong a word, there might have been good reasons for the turban in a different time, I don't see a good one for while riding a bike.
They should just wear a helmet.