Do some graduate students really think that this is all there is to life? Being told by a committee what classes to take, what experiments to conduct, and what direction to take your career?
What about controlling your own destiny? I want to be wholly responsible for my own success or failure. I want to tell people what I do in a sentence, rather than have to explain for 10 minutes how, yes, I get paid to be a graduate student, but no, I don't really make any of the decisions, and yes, my committee holds absolute control over my educational (i.e. degree) and financial (i.e. paycheck) future.
It is a shame that when someone says, "I'm really excited about finishing up and starting the next chapter of my life" the other person doesn't answer with, "I'm excited for you too".