Peter - I understand what you are trying to say. You can't get anymore "water" out of your system, and bigger "hoses" aren't going to increase "pressure/output."
But couldn't you go one step further and even say that a garden hose is the BEST kind of hose to use for gardening and that a fire hose is both cumbersome, sloppy, overkill, etc? Consider watering your plants with a fire hose using garden hose pressure. You wouldn't be able to really water all that well at all. You might even lose enough pressure in the pipe to prevent the water from coming out with even adequate pressure, let alone better pressure.
Now, I know that water and electricity behave differently, but I've heard the "bigger pipes" analogy used a lot to pursuade people to buy thicker cable - implying you can get more electricity/water through them. I've never heard it used in the opposite fashion - (i.e. you've squeezed all the water you can squeeze out of your system by using smaller wire - why waste your money on "pipe" you don't need)....good one!
