> I personally don't see why vision is important

There are at least 2 reasons vision is important in SC1

1. Cloaked units are close to impossible for humans to notice when they are not consciously looking for them but once identified, its relatively easy to track and manipulate them indirectly (e.g. via body blocking). To be fair, I have no idea how the SC1 API works with cloak.

2. Missing short blips of opponent unit movement on the minimap is common and sometimes detrimental enough to swing the game.