Like in machining, there's a long history of measuring everything in "thou" (micro-inch sounds proleptic to me, and you'll see "mil" used in the EDA space). All the tooling uses it, standardized components use it (I can drop a 74-series TTL chip from the 1970s in a modern board), and everyone learns it when they start using EDA.
Recently there has been a shift to metric in EDA software, so you'll see often see multiples of 2.54mm, and packages are switching to metric for the fine-pitch stuff. Often you'll have spacing in both units in the same design.
Not every day these days do I encounter a new word: proleptic.
1 the anticipation and answering of possible objections in rhetorical speech.
2 the representation of a thing as existing before it actually does or did so, as in he was a dead man when he entered. Compare with analepsis: the destruction of the Vendôme Column and his part in it are foreshadowed in moments of haunting prolepsis.
Considering how much manufacturing and science etc. has fully migrated to metric, even in the US, this seems bizarre to me.