How many hard drug users started out on breast milk? The questions are meaningless.
There are many things which are not prohibited, yet we set boundaries and make guidelines to protect against abuses and excess. The behaviors that an addict exhibits usually comes from ignoring the boundaries and indulging in the excesses.
Pot use is on the rise because 1. It is more readily available due to decriminalization on the state and local levels; and 2. Because it is an easy tool escape reality.
When someone is an addict and the prohibited or formerly prohibited vice is now more readily available. Or, if the social stigma of the vice has been diminished or removed entirely. What do you think will happen? Of course they will indulge in the excess.
Therefore, the solution has always been, in our community, to set boundaries, even for permitted things. So speaking about Pot is absolutely crucial and relevant.
A community without boundaries such as the secular world at large will not understand this.