I think, it's the same with giving up your seat; nobody gives up
his/her seat, because everybody thinks somebody will give up
his/her seat. In the end, NOBODY gave up his/her seat.
Classic case of - Everybody thinks Somebody will, but Nobody
did.
IN a situation like this, the first likely thought to come to mind
is; what if it is not a bomb, and I will look like a fool? Or
worst; I'm getting off this bus soon, I should be spared if it is a
bomb...
Same with giving up a seat; What if I gave up my seat and there's
no Thank You?
Generally, this is what I notice of Singaporeans in public. Though,
I believe not all are like that - the less inhibitted ones will be
more proactive; Hey Hey! BC! I think this here bag is a bomb!!!
Quick stop the bus! Stop the Bus!!!