If the apps wouldn’t be slow React Native or whatever “multiplatform framework” crapware, then I’d actually say that well designed, native Swift UI (iOS) or Material (Android) apps can enhance the user experience for a lot of services that are otherwise offered via website. Native integrations with shortcuts, widgets, fully supporting accessibility features of the OS etc.
The problem is most apps are just low-effort web app conversions.
Missing built-in FDE is one of my main gripes with SteamOS. It’s why I don’t really do anything besides gaming on the Deck. It’s a portable device that could easily be stolen or lost, so this seems like a major oversight.