The alternatives are either banning it even for people who are currently physically addicted to it, or leaving it legal for everyone forever. Which would you prefer?

Why should it be illegal?

The industrialised manufacturing and sale of highly addictive (an important distinction vs alcohol) and highly toxic product that is the source of a wide scale multi decade drain on the public health … yeah I can see why we might want this one banned.

After all no one is bitching that they can’t buy their favourite asbestos insulation anymore.

Hmm, let's see if drug prohibition has been tried anywhere and how successful it was...oh.

It will be illegal for all adults eventually. This is just an oddly phrased titled for a ban with grandfathered in exceptions. This isn't a ban for "young people", as there people will eventually be old and it will still be banned.