This is a perfectly reasonable question, and I think there are two aspects to it.

First, one of the research questions tested by Xilem is whether it is practical to write UI in Rust. It's plausible that scripting languages do end up being better, but we don't really know that until we've explored the question more deeply. And there are other very interesting explorations of this question, including Dioxus and Leptos.

Second, even if scripting languages do turn out to be better at expressing UI design and interaction (something I find plausible, though not yet settled), it's very compelling to have a high performance UI engine under a scriptable layer. I've done some experiments with Python bindings, and I think in an alternate universe you'd have apps like ComfyUI as high performance desktop app rather than a web page. Also, the layering of Xilem as the reactive layer, backed by Masonry as the widgets, is explicitly designed to be amenable to scripting, though to my knowledge there hasn't been a lot of actual work on this.

Same reason every other language has UI frameworks. It is more comfortable and nice to write the whole desktop program in the same language.

It's sometimes hard to package a scripting language project to the end-user. Rust compiles to a binary. That's one benefit for me.

Good thing about iced is, you get a compact executable, runs on any OS, looks exactly the same everywhere, perform much better than web based UI, no need to manage any permission to access local files, and you can customize the look as you need, but comes with tolerable default.

Price to pay is building the UI is bit complex as it doesn't hold your hand, unforgiving, and not native.

I like iced. But tauri is good middle ground

If you use a different language you have to deal with some kind of FFI and that's always painful.

Tech wise? If you have your UI in Rust it's both the safest and most performant language to implement it.

And you don't need to ship the entire web stack just to get GUI.