From what I remember, the developer has said that he doesn't want to put much effort into the UI until the very end of the project, because he's constantly redesigning large subsystems and reworking the game mechanics. Any UI tied to any system or mechanic that gets ripped out, redesigned, or otherwise turned inside-out is going to have to be reworked every time that happens. So it gets a barebones UI until the underlying game mechanics are stable.