Just a question of ethics and responsibility.
Honestly, how many times do you think you drove drunk in your jurisdiction? For most US citizens, that blood-alcohol number will be around 0.08, even though states have pretty much moved to 0.06 if you are suspected of major traffic violations (which I think is total BS; just make it de jure).
I would say that there was a period of a few months after I became 21 that I probably drove drunk every week or so. I wasn't blitzed all of the time, but I was probably above a 0.08. In fact, while stunting as a designated driver a few weeks, I've concluded most people leaving bars are probably at a 0.06 or higher, which is why DUI/DWI convictions are such a money-maker. It seems to me our entire culture knows this, but it's all put under the table. Even older colleagues and bosses talk about visiting bars at a younger age and drinking until their liver gasped, and the question of how they exactly got home is never brought up.
I grew out of drinking a lot (although I do still get drunk occasionally and spend time at parties) when I started to experiment with recreational substances. I'm always amused at how alcohol truly impairs you compared to other drugs like opiates, benzos, etc. (when not mixed). It truly is one of the most debilitating substances in existence. Outside of psychedelics or dissociatives, I can't think of anything worse.
Also, what is your opinion about drunk driving compared to driving exhausted, texting while driving, balancing food on the steering wheel, etc.? Do you think, ethically, driving impaired is worse than any of the latter?