The way that crimes are charged and prosecuted is often determined by public sentiment. The more reprehensible a crime is considered to be by the general public, the more likely it is to carry severe criminal consequences (compare child sex crimes with non-violent drug offenses, for instance).
But public sentiment about certain offenses can change over time, and drunk driving is a good example. Although it has always been considered dangerous and a bad idea, there was a time in the United States where police officers were more concerned with immediate harm reduction than prosecution. There are plenty of stories about police officers following drunk drivers home rather than arresting them.
But because of advocacy groups like Mothers Against Drunk Driving, public sentiment about drunk driving has changed. It is now considered highly dangerous, and in most circles, it is a socially unacceptable practice. In recent decades, laws, penalties and restrictions related to drunk driving have strengthened accordingly.
Nationwide, the blood-alcohol concentration threshold for legal intoxication has long been 0.08 percent. Some jurisdictions have discussed lowering the threshold, arguing that driving impairment can start at well below 0.08 percent.
Recently, legislators in Utah passed a bill that goes into effect at the end of 2018. It lowers the threshold for per se drunk driving from 0.08 percent to just 0.05 percent. Law enforcement agencies seem to be supportive of the measure, but many have predicted that they will need to amend the standard protocols for judging whether drivers are intoxicated. Someone with a BAC of 0.05 percent will likely be less obviously impaired than someone closer to 0.08 percent.
Utah appears to be the first state to plan such a change, but they probably won't be the last. As public sentiment against drunk driving becomes ever stronger, so too, will DUI laws and penalties.