Not sure where you're from, but lack of enforcement is not the issue...and neither is punishment. Go sit in a courtroom for a day, you do not get out of dui charges, ever. And enforcement is reactionary by nature, however, there are plenty of proactive measures put in place like sobriety checkpoints and enforcement programs.
Those who end up in court are predominantly ones who either had an accident or were stopped for some unrelated reason. They were not stopped through an enforcement plan aimed at DUI and certainly few are on the water. A very simple thing would be to check everyone leaving a bar at 2:00 AM but that type enforcement has previously been ruled illegal.
As to not getting out of DUI charges, people are given the opportunity to get those charges delayed and/or removed all the time. There are attorneys who are pros in getting people out of DUI's for many reasons. The poor never get out of them but the wealthy do all the time. Furthermore, our penalties are very weak compared to other countries. In France, a .08 is an aggravated criminal offense with 3 years license suspension and 4500 euro fine and up to two years in prison. Most states don't suspend the first time more than 90 days.
Here are a couple of attorney blurbs:
our firm has the experience and training to pick apart the State’s case whether based on an intoxilyzer sample, blood test, or mere standardized field sobriety test (SFST).
No DUI arrest is perfect. DUI law Enforcement officers are human. They make mistakes. DUI Breath Test Operators are human. They also make mistakes. DUI Breath Test Inspectors are human. They too can make mistakes. The DUI breath test machine isn’t perfect. It often makes mistakes and in some circumstances can be flat out wrong. Our Group knows Orlando and West Palm Beach DUI cases. Our Group knows the mistakes that occur in DUI cases and we will expose those mistakes to the judge and jury
Firms like the ones above keep 90% of their clients driving.
While I do not drive while drinking, I have been driving for 32 years and never been stopped for a DUI check. Never a checkpoint. Nothing.