It has everything to do with the metric system. And you got it exactly the wrong way around.

Kilo is simply an SI-prefix. It’s thousand. See: en.wikipedia.org/wiki/Kilobyte. Let me quote that here: “The kilobyte is a multiple of the unit byte for digital information. The International System of Units (SI) defines the prefix kilo as a multiplication factor of 1.000; therefore, one kilobyte is 1.000 bytes.”

That specifically is where the confusion arises. Someone went and said “oh, computers count in binary so a kilobyte is 1.024.” It’s not. A kilobyte is 1.000 bytes, because kilo is thousand.

To help fix the confusion, a different prefix was created: kibi which is specifically for multiples of 2.

The thing is: for people not using the metric system your argument may have merit. But once you have accepted that metric is superior in literally every way (also why NASA etc all use metric), this confusion just disappears.