Ther really is no excuse for it. Unfortunately it seems to us youngsters that it is the older generations which can't practice what they preach as none of my friends would even consider jumping into a car after just one.
I won't let some of my mates drive the next morning. I have got into the habit of stealing my mates car keys and not letting them have them till midday. I get some pissed off mates but they have thanked me for it later.
The trouble with drink drive (and I am in no way condoning this) is that IF you do end up drinking more than you intend to then alcohol has this wonderful effect of lowering our inhibitions and reducing our IQ's to that of a neanderthal (or Chav). All reason and sense dissappears and basic insinct takes over. You will see it any Friday/Saturday night in any large town/city in the UK. People fighting and spewing and generally being obnoxious, things they would never normally do when sober in the vast majority, but once the alcohol kicks in then reason goes so the normal common sense that says dont drive goes and all of a sudden they think they are Schumacher and the best driver in the world when in effect they probably have trouble putting 2 coherent words together let alone drive!