Okay...
Large WASM binaries (especially from GoLang): these take a long time to send over the network increasing loading times. In a desktop app the binary isn’t transferred over the network, so less overhead.
I forgot that you don't have to download desktop apps, they just appear!
Browser incompatibility: Some WebAssembly methods are unavailable in browsers and older browsers are not supported at all. In a desktop app the “browser” is controlled (Chrome for Lorca and Safari for webview), so no compatibility issues.
Electron???
This just seems like you built a less easy to use bundling/development platform than js/webpack/etc and claimed it was better when I'd argue it's way less mainstream and thus less accessible. Not to mention you could've just used native ui like others are talking about. Seems like the worst of both worlds to me.