cartesian direct orthonomed axis system and UE ...

Hello,
I am a mechanical engineer and I wonder why the EU axis system is not direct.
The representation of the X, Y, Z axes on the display window shows that the axes are not direct.
for example, the vector product of X by Y is not equal to Z, but to -Z.
Did that involve anyone? Can someone explain to me why and especially what is the point of doing things backwards?
thank you.