(Nit: it's legal at a state level but municipalities and counties are allowed to dictate more rules on drunk driving - most don't, but YMMV)
But you can certainly have one beer on an empty stomach, have a BAC of 0.04 and drive around. As long as you aren't visibly impaired, it's legal.
Anecdotally, I feel like it's actually gotten less common over the years. When I was a teenager I would meet adults who were riding the bus because they'd had their licence taken away. Often it would be for a 6 month period before they could re-apply (without retaking the test). That became less frequent at some point.
But yes, it is somewhat common for people to have an idea of what it takes to get to a BAC of 0.08%, because that is the threshold at which you will be charged with DUI. For many regular drinkers, they won't be impaired at 0.08% and it takes less alcohol than you think to get there. Especially with modern microbrew beers. Getting a DUI will completely f*ck over your life, so if you like to drink socially, you are very careful.
In England and Wales, a drink-driving offence would attract a minimum of a 12 month disqualification unless there are very compelling mitigating factors. On a second offence (or a serious first offence), you would usually have to undergo a medical examination and re-take your driving test to get your license back.
https://www.sentencingcouncil.org.uk/offences/magistrates-co...
https://www.gov.uk/driving-disqualifications/disqualificatio...
https://www.thisismoney.co.uk/money/cars/article-10304829/Mo...
I know someone who was woken up by a State Trooper, fast asleep in her vehicle on the side of the road, with the engine running so it was obvious that she fell asleep while driving.
It was by far not her first DUI. I assume that she lost her license after that, but I do know that she kept driving.
It doesn't sound obvious to me. If it was cold out, you would run the engine for heat for instance.
I also neglected to mention that the car wasn't neatly pulled over onto the side of the road but had driven itself into the ditch between the road and a field.