How come we can’t see light before it’s reflected off something?

Answer

The essence of your question is really: “what is seeing?”
Our eyes are receivers, not transmitters. They receive photons from the directions in which our field of view is pointed, and our brain creates an interpretable image from them. When light shines on an object, the photons will be reflected, and eventually photons will enter our eye. Because we have two eyes, our brain can combine both images and give us a correct idea of ​​distance. If there is no bouncing object, photons will simply fly past us and fail to reach our eye.
That is why it is pitch dark in space: although photons are constantly flying past the astronaut, there is nothing that can reflect them. So if he sets his eye on a point next to the sun, he will not receive any photon from that direction and he will interpret that as “black”.
On Earth, the situation is different: the molecules of our atmosphere reflect the light particles from the sun in all directions, so that we can receive them from all directions.