You think it is all convenient and easy to use intuitively, until i ask you, to convert how much water you use a day to how much water you use in a year and how much water your city uses.

Because your city measures in acre foot, which is 43,560 cubic feet or 325,850 US gallons. Actually there is a weird 3/7 of a gallon left

So you have no way of relating the ~20-40 gallons of water you use per day to the water use in your city ir the water you use in a year that is measured in centi-cubic-feet without pulling out a table and calculator.

Meanwhile i know that i use about 120 liters of water, which is 0.120 m3 a day. So my water bill in m3 is just a thousand liters per m3 and my city uses 230 million m3 a year or about 630.000 m3 a day. With that i can easily estimate that i use about 1/5.000.000 of my citys water.

So when we are talking about drought issues, or water demand etc. i can understand the values in the scientific and political debate, because i can actually relate them to my personal life.

The metric system empowers people because it makes SI units in any domain and of any size relateable and accessible. Meanwhile a kid in the US doesn't know what a mile is until it learns that by being driven enough miles to get a feel for how many yards that is.