In one of Heinlein's books he makes a similar point about guns. As I recall, he argued you'd be better off unarmed because you'd feel more paranoid and would avoid the dangerous situations where a gun would help. If you have a gun, you need to guard against any sense of invulnerability. (Heinlein has made pro-gun arguments in other books. I don't intend to start a gun debate here, but just to give a perspective on the original question.)

However, I think a short-term BoB would mainly be a benefit. It'd help keep you alive and so give you time to adapt. Bootstrapping. For example, you could use commercial cordage to build a shelter, and then sit in the shelter while you figure out how to extract natural cordage from plants. There's a danger that you might decide you don't need to figure it out because you have your commercial cordage, but in an EOTWAKI scenario hopefully you'd know you were in it for the long haul and wouldn't get complacent.