The playing area is small to account for the heavy amount of vertical content, and to ensure cubes that fall actually get a chance to interact with the layer around them. Not to mention, we don't want height accumulation to be a slog.
The text space is large as the game features a heavy amount of text and reading compared to most roguelikes. The text in general is large, as again, there's a lot of reading and I would prefer to avoid eye strain. That said, you can change the font size in settings.
The game, ultimately, isn't exactly a roguelike, though it shares some aspects such as being text-based with heavy reliance on procedural generation. Permadeath is optional, you aren't crawling a dungeon, the genre is survival, and for the most part, the game runs in real-time.