While I am no apologist for the measurement system we use here in the United States, I realized something interesting when trying to explain why almost all of our units consist of easily divisible sub-units. Imagine you needed to split something up into halves, thirds, fourths, sixths, etc.. If you imagine doing this with paper, it's fairly easy.

Now imagine Metric, and the need to split something into 10 even pieces. We can make this a little easier knowing that we just need to split into fifths first, and then halve each of those. Do you know how to fold a piece of paper into fifths?

It can be done, and it's remarkable how to do this with a straight edge and a pencil. However it is definitely more time consuming than being able to fold using easily divisible numbers. To that end, once you have a decimal ruler you can just use that, but I can see why decimal based measurements were not more common in the past.

All that being said, I really wish metrication had been completed here in the US before I was born.