What is the name of your state? TEXAS
I've never actually gotten a DUI but i read that you should never consent to take a breathalizer.
The reasoning behind this was that 94% of all cases that dont have a breathalizer test to back them up are thrown out. Also that when you refuse to take the test the worse a cop can do is impound your car. So he figured that paying $200 to get your car out of impound is better than jail time and a $3,000 fine.
Now im sure they could do blood tests as well....but again, how could they forcefully stick a needle in your arm without your consent. Besides, by the time they actually got yu ready to have your blood drawn im betting you would have sobered up.
I think this would mainly just apply to those drivers that are only slightly under the influence....but still enough to be arrested.