I don't get this, what is wrong with unwrapping. The map doesn't need to be perfect.
Are you being realistic ? Try unwrapping already "baked-down" high-poly meshes like sofas or complicated chairs. Plugin or manually, it's tedious process, and every mistake shows as ugly black seam, lowering substantially visual quality.
And yes, quite to contrary of texture maps, lightmaps unwraps need to be as close to perfect for the GI as possible.
Yes, everyone can unwrap few box walls, that's not where we're getting at. Big scene with thousand of assets, lot of the high-poly hero assets, not so much.