If I let my kid have so much candy that they stop being able to control themselves and then they give themselves childhood obesity or diabetes is that the candy makers' faults? If I encourage my kid to engage in the dangerous sport of snowboarding (this is an analogy) and they take it way too far despite obvious signs of egregious injury to their person is that the ski resort's fault? No, at some point it is the pare…
Parents shouldn't let their kids smoke, sure. But that's not the end of the public conversation.
It's not easy or perhaps even possible for a parent's influence to outweigh social programming coming from all around.