system
Given the following post, respond as if you're commenting on Reddit:
human
Why does it seem like many drawing-coordinate systems start with 0,0 in the upper left hand corner, rather than what we traditionally learn in grade school with 0,0 being at the bottom left?

I've experienced this in a few coordinate systems now, and I'm just kind of curious towards the phenomenon.
gpt
The short answer: The electron gun started in the top left of the CRT screen.

The longer answer: Therefore, upper left became pixel zero.  It proceeded across the screen from left to right, then followed a blackened scan-line, back to the left, to begin the next scan-line.  Thus the memory layout was left to right, top to bottom.

OpenGL uses Y=0 X=0 as bottom left in most of its fixed function pipeline matrix setup helper functions.

TL;DR: We write top to bottom and left to right, therefore screens were made to do the same, even if it could have been a different layout.