No disclaimer necessary. Police officers have a lot of latitude in who they let go and who they ticket or charge. The officer in this case may have assumed that the author wasn’t in the habit of driving drunk and figured that he didn’t want “one mistake” to haunt her forever. A few decades ago, cops were even more flexible about this stuff because drunk driving wasn’t taken as seriously as it is now. And of course the possibility of getting charged depends on the driver driving in a cop’s line of sight in the first place.
As for the possibility of injuries/ death, the truth is that lots of people drive drunk, and most of them get home okay without hurting themselves or anyone else. Drunk drivers are okay the majority of the time. That’s why so many people are able to ignore the seriousness of the situation; they made it home just fine the last time, after all.
None of this is to say that drunk driving is a good idea, of course. A person who drives drunk just once can easily get charged or kill themselves, their passengers, or other people on the road. But drunk driving isn’t bad because consequences are likely; it’s because the potential consequences are so serious that even if they’re still low, no one should put himself or others at risk of them.