As George Orwell wrote, a liter is too much and a half a liter is too little. There are many other problems I find with the metric system that make it unintuitive for daily use by most people.
What do most people use that is a meter long? broomsticks? What good is a millimeter to most people? Even a single centimeter is too little to be of much use for most practical purposes.
In contrast, a foot (about as long as your wrist to your elbow) has 12 inches and can be divided into 2, 3, 4, and 6 inch fractions. 10 can only be reasonably divided by 2 and 5. Also, and inch can be divided into 1/2, 1/4 1/8, 1/16.... This is not so practical with centimeters. For example, I have a one foot ruler on my desk with 1/32" units on it which is just as useful as millimeters for any practical purposes.
I can also fit a one foot ruler in my bag and still have a useful measurement that is neither too long nor too small to be practical.
I can look at the monitor on my desk and "see" that it is about 16 inches tall, but if I did that in centimeters I would have to use "big" numbers such as 40 or 41 to make the same estimate. It's a lot easier to deal with smaller numbers than with big ones that only exist to accommodate the meter. This is probably why people are reluctant to say how tall they are in centimeters as opposed to feet. For example I am 5 feet 9 inches tall which is easy to relate to; just look at my height and try to divide up it into 5 3/4 of some "unit", that being a "feet". Then try to dividing my height up into 180 equal units (centimeters) by just eyeballing me. Inches and feet are just far more "intuitive" when it comes to dealing with real objects. It doesn't matter that there are 5280 feet in a mile. Unless you are an engineer you probably don't have any reason to consider how many meters are in a kilometer and probably don't ever give it much thought. Most people would say "1 and a half kilometers/miles" and never even think of having to convert to anything else, i.e. meters, feet, inches, Hersey Bars...
Back to Mr. Orwell. What good is a liter by itself? I cannot drink a liter of milk in one sitting, drive very far on a liter of gasoline/petrol and it's not worth my time to carry a one liter bucket of water out to the sheep. The liter is just either too small or too much for any practical purposes....
The gram is too small the kilogram is too much for practical purposes. There are 16 ounces in a pound. The gram is unless unless you are selling or buying drugs, so why have to use it in daily life?
I don't want four-hundred fifty something grams of meat, just give me a pound. I might not want a kilograms of banana either, but a pound will do and if I want more than a pound or sugar I might take 2 or 3 of them plus 1 to 15 ounces. Why do I suddenly have to start dealing with hundreds of grams when 1 to 15 of something more "handy" will suffice?
I won't even get into temperature......
Anyway, I am not saying the metric system is a bad thing. It's great for science/engineering and it makes converting between units very easy, but most people do not perform the type of conversions in their daily lives that the metric system makes easy and forcing them to use individual units that are by themselves either too small or too large is rather pointless. Anyone who needs the metric system is already familiar with it. And as a previous poster put it in another thread, anyone who has a problem with it should be hit with a two-by-four.