Later on, stone floors normalize small uneven dirt surface to make it totally flat and much nicer. Stone also lets you put fire on it. Wood, the primary reasons to put down a floor are snap points (so you can have aligned walls easier, if you do interior walls) and the look of it.

If doing ultra compact builds, you can floor over holes that contain annoying things like workstation upgrades, chests, or the like.

https://steamcommunity.com/sharedfiles/filedetails/?id=2775728477