It matters enormously to a successful democratic society like ours that we have three branches of government each with some independence and some control over the other two. That's set out in the Constitution.
My senior year of high school when I was getting recruited for college my dad goes to me 'You can become an Olympic champion.' And that's the first time that I'd heard someone else say that to me. I was like 'Uh are you talking to me?'