[tommiegannert]

> Components often still use 0.1 inch pin spacing.

This changed with IC SMD packages. It's now mostly even 100-micrometers.

SMD passives seem to be in a state of limbo, but mostly still using inches. Mouser lists resistor size codes as both inch and mm. It's a bit confusing.

[rcxdude]

yeah, PCBs are a muddled mix. I've seen footprint drawings which use metric for some dimensions and imperial for others!