Walls aren't just for practical reasons, they are primarily used by a bunch of the community for decoration, could be expanding existing things like adding onto the desk or even making an entirely new structure somewhere out in the world.
You do need to remember this is also a sandbox game where you have the freedom to decorate your base, things like this don't necessarily need an obvious practical reason to exist.
The hot plate was added before the microwave could properly cook raw food and before any of the other ways to cook food were added, so it is kind of obsolete at this point as everything else is better than it, but they also can't really just remove it now because it is a feature that some people use.
Viewing post in Voices of the Void 0.8.2 feedback
With all the weapons being worked on, to me - it seems that walls are mostly for building defensive bases.
I just hope that game would continue to retain its eerie horror spacey creatures style, and not turn into a survival game (with all of these fishing, cooking, chopping trees, farming plants, farming honey, etc features).