As a child/teenager, I hated those words. It seemed like I heard them all the time (probably only 4 or 5 times though) Whenever I asked WHY, I had to do something (e.g. wash dishes, cut grass, make my bed, etc.) I wasn't given an explanation, I was just told "because I said so."
Most often, these words came from my dad. I'm sure they came from mom on occasion, but I can't remember any specific case. Actually, I can't remember any specific case from my dad either, I just know I heard the words and grew to hate them. At some point, I decided - I'm never going to say that to my kids!
My first-born arrived in the early 1980's. My wife & I both had college education (which we thought was the answer to everything) and we agreed we would not use those words. We knew that we could work with our child, explain the reasons and come to a reasonable agreement on what could be done and what should be done. Those of you with children are laughing right now.
When it was time for bed, the question came out - "Why?" We explained why they needed sleep. "Why don't you go to bed?" Because I'm an adult. "Don't you need sleep?" Yes, but not as much.
Of course, the conversation went on. And it wasn't necessarily about bed. It was about any subject that came up. Eventually, I'd get tired and my answer was "Because I'm the Dad!" (it wasn't the words I'd sworn not to use, but it was close).
Eventually, I realized that some subjects couldn't be reasoned out. No amount of discussion was going to convince them that I was right. No amount of discussion was going to convince me that I was wrong. We didn't have to agree with each other, we just had to respect each other's positions and move on.
More on this subject next time...