it hid the fact that real-time global illumination wasn’t a thing yet
I don't see how that follows.
Having more than like 1-2 runtime dynamic lights (usually a flashlight) didn't become somewhat common until like late 2010s, and pre-baking a shitton of light maps to simulate things like lights turning on or moving goes all the way back to HL1 if not quake.
The number of lights isn't the thing, it's the color bleed between adjacent objects. Like if you look at a Cornel Box Model, the way the white wall is a little red near the red side, because it's picking up reflected light from there. That's a subtle thing that'll make your scene look wrong, but it's a lot harder to notice if everything is brown.
Pre-baked light maps have accounted for colored light bouncing and mixing at least as far back as HL1, but I think the compile tools of the time did something weird like averaging out texture colors or ignoring them all together.
It was a computational issue, dynamic lights are expensive to calculate at runtime, fully prebaking multiple dynamic source requires you store exponentially more data for each source to account for all the ways the sources can interact if you don't want to do any lighting calculations at runtime.
I don't see how that follows.
Having more than like 1-2 runtime dynamic lights (usually a flashlight) didn't become somewhat common until like late 2010s, and pre-baking a shitton of light maps to simulate things like lights turning on or moving goes all the way back to HL1 if not quake.
The number of lights isn't the thing, it's the color bleed between adjacent objects. Like if you look at a Cornel Box Model, the way the white wall is a little red near the red side, because it's picking up reflected light from there. That's a subtle thing that'll make your scene look wrong, but it's a lot harder to notice if everything is brown.
Pre-baked light maps have accounted for colored light bouncing and mixing at least as far back as HL1, but I think the compile tools of the time did something weird like averaging out texture colors or ignoring them all together.
I know HL2's compile tools accounted for the color of textures better, though they still did some weird things.
It was a computational issue, dynamic lights are expensive to calculate at runtime, fully prebaking multiple dynamic source requires you store exponentially more data for each source to account for all the ways the sources can interact if you don't want to do any lighting calculations at runtime.