It’s not about being normal. This data is for scientists. The denomination was a deliberate choice given the various sizes of the data. It might be as low as single digits in some cases.

We use decimals all the time. We’re not dumb. But when making direct comparisons of values, it’s a simple fact that comparing 5 to 20 is easier than comparing 0.05 to 0.2. This is a scientific fact. It’s easier for your brain to parse. You can’t deny that. Go ask a psychologist. In addition, the data is cleaner. It’s easier to print “5” than “0.05”, and then you mention the denominator under the graph or table of data.

Every engineer and scientist in the US uses metric, and it doesn’t matter what the average person uses. Proper home cooks find bread recipes with metric weights for ingredients, for example. Woodworkers use feet and inches. People who use the Imperial system are just people using what they know. It’s entirely moot to this conversation. I don’t know why you keep bringing up fractions and the Imperial system as if that adds any weight to your argument about the actual topic at hand. The topic being scientists using a deliberate unit of measure to make it easy to print values and compare them at a glance.

Who said anything about fractions? Whole numbers are easier than decimals and fractions.

And no, this isn’t just a US thing. I’m certain your country uses things like “parts per million”.

Because it makes the numerator whole numbers for all data for easy comparisons by human minds. Comparing 300 to 5 is easier for people than comparing 30 to 0.5. It’s the same reason machinists use inches per minute over inches per second. It’s so values are between 1 and 600 and not between 0.0176 and 10. It’s easier to reason about whole numbers than decimals.