I didn't say that at all.
Certain things are good for one thing but not as good for another. Basing your metrics off of water and light make a lot of sense when you have to measure a great deal of new items and compare them objectively.
On the other hand when you need metrics to be a guide through daily life and nothing else, the system that's born from daily necessity makes a lot more sense.
Daily necessity? Is measuring your foot a daily necessity? I don't get what you're trying to say here.
Some defenders of the Imperial system tell us it's handy to measure in body parts, presumably because you all have them. But what percentage of US citizens honestly have foot-long feet? Perhaps half a foot should be called a penis? (Credit to rdowns for that idea.)
The reasoning gets worse when you'd ask 311 million to make a change because a smaller community of professionals would like their standards to be the standards for all of society. It's not like the two can't coexist; there might be a good argument there if the two were incompatible, but the fact is that they're not.
Can't you concede that there is a benefit to having a single 'standard'? The two are only compatible in the sense that you can convert between them if you know the conversion factors. Every time someone has to do this, they are wasting time. Multiply that over 311 million people and you have an awful lot of wasted time!
A distinction needs to be made here: just because something is easier to multiply by 10 (or 1/10th) doesn't mean that it's easier to use. How many times in your daily life do you need to multiply by 10 …
You multiply or divide by a multiple of 10 every time you need to convert from one derivative unit to another. 'Kilo' means a multiple of 1000 over the base unit. So if I need to convert from metres to kilometres, I simply divide by 1000. Now, that happens to be very easy to do. Why? Because our whole system of counting is base 10! It's as easy as moving the decimal point three places.
… or even multiply what you measure?
It doesn't matter what operations you're doing — multiplication, division, addition, or subtraction — it's as easy as manipulating any decimal number. You never, ever have to remember odd conversion factors to convert between different units and fractions thereof.
How often does that easy arithmetic come up outside of science? Can you think of a real life example?
I do a bit of carpentry and other work around the house. From time to time I'm buying lengths of timber, so I may be multiplying a required length over the number of lengths required, or adding up different lengths. If you're a cook, no doubt there are times when the recipe serves 4 people, but you need to cook for 6 or 8 or something, so you have to multiply measurements. When I used to go swimming at my local Olympic sized pool (which is 50 metres long) it was easy to calculate how far I swam. 20 laps = 1000 metres = 1 kilometre. I mean, I could go on and on giving you everyday examples if you want me to, but I think you're capable of doing that yourself.
I don't think Tomorrow ever responded to my earlier hypothetical, so let me put the same question to you:
Okay, imagine for a moment that one of the US states wasn't using the decimal system for counting. Instead, they had a system where letters were used to designate certain amounts, similar to Roman numerals, but instead of having a base of 10, it varied. So perhaps A is equal to 12. Then three As is equal to B. Two Bs is equal to C. 22 Bs is equal to a D, and so on with this kind of inconsistency. You have a friend living in this state who claims that the system works just fine — he spent many years studying this system and even more using it in his line of work and can't see why he or anyone else in the state should have to learn this dangfangled decimal system. What would you say to your friend?
In any case, I do already have it. It's on every measuring device I have, from my ruler to my bathroom scale. I use it when it's necessary or more effective, but that's rare. Maybe you should accept that people can have a different preference.
But (1) it's not your first 'language' so to speak, so you're no doubt less comfortable with it, and (2) if no one else around you speaks the same 'language' it doesn't help you communicate with them. This is why we have 'standards'.