It's also a peculiarity of kilograms. The kilogram rather than the gram is the SI base unit for mass.
Thus it's normal to use e.g. 1e6 kg rather than 1e9 g.
Thus it's normal to use e.g. 1e6 kg rather than 1e9 g.
OTOH, 1KHz has no basis in physical reality for normal people but they know 1KHz is 1000x faster than 1MHz so it works nicely for things like "is my new computer faster than my old computer" (at least a decade ago, I don't see clocks advertised much at all anymore).
It stops on the ton, though - “40 thousand tons of grain” - gigagram isn’t used.
Re kHz, I think most people understand frequencies we can hear. (1 kHz is close to a high C note). MHz and GHz are radio frequencies.