From my experience, thirty years as a cop, and my opinion, it has a lot to do with the pervasive cultural of alcohol. Some of our judges were famous drunks and it was almost impossible to get a trial much less a conviction. Deputy D.A.s often didn't take drunken driving seriously for the same reason. Then there were the legislators. When I first started we had one, a state senator, that the police routinely drove home and delivered his car after he was stopped driving drunk. The City Attorney was also a drunk and got a pass. An officer arrested a drunken driver who called a buddy in the Elk's Club and a few minutes later a Deputy Chief showed up the tear up the ticket and escort his friend home.
We went through a period where we had to read a page, in Spanish, to every drunk driver before they were given a breathalyzer or blood test. It didn't matter whether they spoke Spanish or not. We had a lengthy questionnaire to read with questions like, "What city are we in right now?"
[omitted]
If it gets to a jury, most of the people on the jury have driven drunk at least once. The defense attorneys go heavy on how the poor man was celebrating and didn't realize he was drunk because he didn't drink often. One defendant, a sheriff's deputy, got off by saying he was a teetotaler and didn't realize the drinks he was being given had vodka in them.
Our city at one time had the highest per capita DUI arrests in the country. Drunks started leaving town to drink. I was working downtown one day and got a couple of hot dogs from a push cart and sat down on a bench to eat them. I was joined by two construction workers. One said, "Harvey here got a DUI ticket not long ago. How you feel about cops, Harvey?" Harvey surprised his buddy by saying, "They're okay. I was drunk. And when I went to the mandatory program they have I met two bankers, three attorneys, and a judge. I don't mind getting caught as long as everyone else gets caught, too, and these bastards nail everyone." We laughed and I said it was true. People don 't mind being nailed if they know the state senator, the City Attorney, the judge, and members of the Elks Club get nailed, too.