The police try to tell people, or they try to tell the courts, or they try to tell you if you've been arrested for DUI that field sobriety tests, the walk-and-turn, the standing on one leg, the finger-to-nose are standardized tests. They're really not. They're just kind of made-up tests, and they're not very indicative of whether or not you're intoxicated.
I think that if you know you've been drinking, you probably shouldn't take them. However, you will be arrested, and you will lose your license. However, by taking them, if you are intoxicated and you do look intoxicated on a videotape, you've just provided the state attorney with a large piece of evidence to prove the case against you.