The reason being that Open Source is a bunch of people who approach EVERYTHING as a programming problem, and they are chronically allergic to graphics, graphical UIs, and any kind of sense of what user interactions are a good experience.

They don't start with "how do users want this to operate?" They start with a weekend of coding, applying their preconceived notions, a library of fancy algorithms that are not directly motivated by an actual feature, and they go from there. This does not lead to a good product, as in something that could earn you money on an open market. It only prevails, in spite of nobody wanting to pay for it, because they give it away for free, and they sink their own "disposable time" (and maybe even income) into the project.