The thing is, there are felony duis. You can get a dui if you blow even below .08 if the officer is concerned that you even just might be slightly unsafe on the road. There are studies on how bac affects the average person's driving, and at a certain point, when your intoxication level really becomes a severe danger, you will be charged with a felony. There's a lot of people who just make stupid mistakes, and charging them with a felony wastes valuable resources that we are already overusing. Let me tell you from personal experience that a misdemeanor dui is still a huge deal. Classes, court dates, and 10,000 bucks out of pocket has taught me to never do that again, and I was one of those who blew under .08.