It's easy. The text is marked up, mixed in with images, video and other miscellaneous rich content, and includes remote resources and third party embeds.

There is no native UI toolkit that can do this properly, nor is there a cross platform way for 3rd parties to integrate even if there was. So web it is, with a runtime designed for being able to rapidly page in/out the entire UI from one screen to the next, even if that is entirely unnecessary for a single app.

Grouches have been shitting on the web, not entirely for bad reasons, but it's made them miss the fact that web has been stealing their lunch for a reason. If you live inside a terminal, your needs have diverged from the majority, and you're likely relying on crutches that are considered impossibly clunky by most.

The only ray of hope here is what FB has done with React and React Native, but I imagine it will take another 10 years before the unix geeks will want to admit there is something in that "webshit" worth looking at.