Except many parents understand and accept that their teenagers go and have some beers or drinks with friends; as long as they do it as safely as they can. And of course this sort of approach to it - rather than the heavyhandedness some parents apply - means your children are more likely to trust you enough to, say, call you for a ride home rather than drive drunk, or otherwise come to you if they have a problem.
Anyway, it's a bit silly to compare having a cellphone (what GP was talking about) to regularly consuming alcohol. Sure, maybe social media is the equivalent, but then, those might be the "dangers" I talked about.
You are missing the point of just how impactful "media" is on people's minds. It may even affect you so much that you either don't realize it or do not want to realize it. It is most apparent in America, but it has spread across the globe, where people's whole world view and mental framework is materially impacted by what they see in movies and on TV in general; they think cars explode when you shoot at them and you can take shelter behind them from bullets, they scheme and connive as if they are on Survivor, they style themselves and speak and quote things form TV and movies, they take queues on how to be, live, act, and even parent from sitcoms and movies, they have delusional senses of romance, sexuality, and relationships... the list is long.
You may not recognize it as alcohol and you make make the laissez-faire argument, but it is really kind of irresponsible even if you do it. Permissiveness should not be the response to detrimental things, especially with what all else happens in environments related to and gateway by alcohol permissiveness.
Interestingly, nobody I know falls into those descriptions... Still, I don't deny that media has an impact on people. That's not really the question though, is it?
Nor is it a question of unqualified permission. My point was that strictly disallowing some things tends not to work, while the opposite - not permission, per se, but reluctant acceptance that it's going to happen anyway - will at least allow children to come to their parents for help, as opposed to hiding it.