This is a real question. Bans "seems" to me as an efficient tool, but I have no source either...
But also, we prohibit lots acts that are harmful to others, instead of taxing them. It's also a moral thing. Values are changing and increasing share of people are seeing unnecessary emissions as a wrong.
Taxing liquor would have been a far better approach.
A clear well defined ban seems more efficient and straightforward, as long as it can be enforced. In this case - unlike for prohibition - it can be enforced like you point out.
Using some other random website, the same trip for one person on train is calculated to be 2kg.
So that makes it a factor of about 100x. How much could the tax be that would still make it distinguishable from a ban? How would people react if say the tax would be 1€ per kg?