Just reckon some people wouldn't be very safe after even one beer, but general perception is that one or two is ok. These people probably dont realise they are crap drivers.
There are also plenty of people who are not particularly crap drivers, but they are not really good drivers either. For example, how many people that you see on the road actually know how to control a spin?
This has only happened to me once on the road, hit an unseen patch of diesel, I wasn't speeding, hadn't been drinking, but fortuantely I knew exactly what to do...a mispent youth playing with gearbox karts and bigger toys definitely saved me !
The reality is most people have never experienced geting even close to the limit of control, until its too late.
And then we say its OK to have 1 or 2 beers as well.....
If everyone had perfect vision, excellent reaction times, good road awareness, great car handling control...then maybe it would be OK to allow 1 or 2 beers over lunch. Think I'd still stick to coke though