CAD used to be digital abstraction of the physical media that is 2D drawings on paper, so XY is the plane of the paper going horizontal/vertical, and most detailing are in vertical cross sections so Y ended up being up most of the time.
The Z axis is then Frankensteined into the existing system to get a proper 3D representation, so it became the depth axis for the existing XY plane.
In Minecraft it’s even more evident as Notch Frankensteined the Z axis into a game engine that’s originally developed for side scrolling.
CAD used to be digital abstraction of the physical media that is 2D drawings on paper, so XY is the plane of the paper going horizontal/vertical, and most detailing are in vertical cross sections so Y ended up being up most of the time.
The Z axis is then Frankensteined into the existing system to get a proper 3D representation, so it became the depth axis for the existing XY plane.
In Minecraft it’s even more evident as Notch Frankensteined the Z axis into a game engine that’s originally developed for side scrolling.