FOSS gamedev and creative worlds

Hello,
just a random question that I have kept for years:

Why in minetest are y and z reversed? In all maths lessons I had and in all games I have played, x and y were always used on the plane and z is used for height.

Is this by choice? and why?

(don't hesitate to correct my english, i'm french).

On computer, X is usualy on horizontal axis, Y on vertical axis and Z stands for depth. I guess minetest coordinate system inherited that.

It's because the screen is vertical, and is the x y plane. Nearly all games and rendering engines use this convention