It gets even more interesting when aviation uses:

• feet for vertical distances – such as 1000 ft overhead separation for aircraft heading towards each other
• meters for horizontal distances, such as 1.3 km between two aircraft going for landings on separate, parallel runways of the same airport
• statute miles for visibility ahead of the aircraft, such as when fog is ahead
• nautical miles for distances to waypoints and navigational aids

The bizarre thing is that these are all conventions that stemmed from good rationale, at least initially. Using meters for horizontal distances means it’s hard to confuse it with vertical distance, when speaking over rough radio comms. Statute miles is what the meteorological agency in the USA would report, and ATC provides that information to pilots. And nautical miles, as the name suggests, has a rich seafaring tradition, which aviation adopted wholesale.

It’s why aircraft have the red (left) and green (right) navigational lights, same as ships do. It’s also why the “rule of the road” for two intersecting aircraft is for the right-hand aircraft to go first, since their pilot sees the other’s green light, while showing a red light to the halting aircraft.

TL;DR: everything boils down to: “it’s how we’ve always done it”