Restricting eating and drinking on the Metro is a conditional prohibition, with a condition of place that's very narrow, and of time that's very short. That's very different from making something illegal in general, in private, at all times and all circumstances.

The first is easy to accept because the limitation is easy to escape. The second is much harder to accept because the law is reaching far into private spaces and private aspects of our lives, all day, every day. And with that comes the purported justification for monstrosities like dynamic entry raids. That purported justification is very circular: Because you could have drugs only in your private space, you might be able to destroy them before they can be seized. And that drives malign legal philosophies that claim that supposedly valid warrants can reach anywhere. Without a Drug War we would not have 90%+ of the SWAT teams, routine dynamic entry raids, police militarization, and super-aggressive plea-bargain driven "justice." Nor might we have questions about whether we should have reliably private communication and data storage.

You are not counting the extent to which drugs have rotted the law from the inside. Never mind the anti-freedom thing, the Hobbesians ought to try and hang the narcs for poisoning Leviathan herself.