SE isn't fully 3D Voxel though. Only the structures are voxel. The landscape is a moldable mesh with no SI calculation data.
There are backup files in the save that you can use to recover. You just have to utilize them after the crash, and before you load the corrupted save. Again, instructions on this are in the Pinned FAQ thread. As is a workaround that may work if you loaded the corrupted save and broke all the backup files.
If they were to progressively save your game, you would end up using several gigabytes of disk space for each save. For an older computer, this would essentially pause game progress for a minute or two while the save occurred. It doesn't come down to a matter of common sense. It comes down to how the data is managed, and the limitations of supporting older hardware. In your 30 years of gaming, you haven't come across a game yet that handles as much raw data live as this one does.