I completely agree.[
Ditto...
For example, if you only need 5gpm, then 1-1/4 is already more than big enough and going up to 1-1/2 is just a waste of $$$ on buying larger pipe. From a cost perspective, you want to TRY to use just 1" pipe because it's so common that even if you could reduce to 3/4", the cost difference between 3/4" and 1" isn't that great. But once you get above 1", prices jump pretty severly. But if you need 20gpm at a point 200' away, then yea, you might need to consider upsizing the pipe.