To many faced with "you can be whatever you want" don't want to do anything; all they "want" is satisfaction of basic urges and amusements. Pressured to attend college or get a job, they perceive "do whatever you want" as picking a marginally satisfying term from a menu, and dutifully showing up for class and assuming a job will somehow follow.
Those who "do whatever you want" are going to do it regardless. I write software for a living because software is my life: I'm going to write software no matter what, I did it compulsively from an early age, and got good enough at it that someone wanted to pay me to do it. Michael Dell and Bill Gates and others dropped out of college because it got in their way of compulsively creating technology businesses. Eminem spends every spare moment writing lyrics, and if he has no paper he'll scrawl them on a wall.
"Be anything you want to be" only works for those who have a want, not for those who don't.