I have never, in around four decades of living, had an actual need to determine the mass of a given volume of water, or the volume of a given mass of water.
When cooking, I routinely need to split some quantity of an ingredient into thirds or quarters.
Yet I am also constantly told that I'm ignorant and backwards and irrational for preferring a system that optimizes for the latter, rather than for the former. Base 12 is genuinely better for many real-world applications than base 10, those applications are more common in the lives of non-scientists than the applications metric is optimized for, and I doubt you're going to be able to produce a rational argument otherwise.
But that's because your recipes are built on the easy divisibility, no? If your recipes are built on weight measurements, suddenly "easy divisibility" brings nothing to the table. If you cook with a kitchen scale, "one ml of water is one gram" is used all the time.
So you never went hiking for a longer period of time or did anything that actually involves carrying water.
I remember when some guys thought about building a pool on the balcony, calculating how much water weighs is admitably not ver often used, but when it is the consistency of the metric system is nice.
I work with wood in mm for years and never had any problem with the metric system. Finding the third, fifth or sixth or whatnot is not hard if you are used to it at all. Converting from mm to meters isn’t hard, etc.
Having a number like 666.66 mm probably sounds scary to measure (beyond the religious connotations), but in fact it is a point on a line that is easy enough to find.
I have never, in around four decades of living, had an actual need to determine the mass of a given volume of water, or the volume of a given mass of water.
When cooking, I routinely need to split some quantity of an ingredient into thirds or quarters.
Yet I am also constantly told that I'm ignorant and backwards and irrational for preferring a system that optimizes for the latter, rather than for the former. Base 12 is genuinely better for many real-world applications than base 10, those applications are more common in the lives of non-scientists than the applications metric is optimized for, and I doubt you're going to be able to produce a rational argument otherwise.