You can get plenty of weird ideas while you’re falling asleep. And weird ideas—or unexpected, if you like—are what you want if you’re an artist. But execution is missing. You’re tired, drifting. It’s nearly impossible to bring an idea to reason, never mind fleshing it out.
But ideas are valuable just to keep handy. They’re easy, fruitful, and full of possibility. That’s all they need to be on their own.