Why do you need a beautiful UI? Because you need something to use for thousands of hours.

Why have a visual interface at all? It’s more convenient to use, is way more engaging, and just better for learning. There is an audio component to the app, and I’m sure more and more audio components will be added, but I would be surprised if in-app audio ever exceeds half of my usage.

For example there is a shadowing exercise that is purely audio based (put in headphones and press play). But what if you want to see what a word means? Or see its gender/case/tense? Mark it as easy or hard, remembered or forgotten? I can look all this information up, plus read a few paragraphs of explanations in less time than I would take me to formulate a question.