I too wish that software would be efficient, robust and long-lasting. But it seems that most people don't care about this enough (compared to other factors) to force change. (Alternatively, they are locked in to platforms they don't like to use.)
Which one exactly ? IE ? Dillo ? Lynx ? Pale Moon ? Firefox version 126 ?
Alphabet make money from ads, so they want web pages, apps on Android and Chrome everywhere.
Mozilla make money from Google.
Microsoft make money from software licenses and subscriptions and from cloud services. They might be interested in cross platform installation.
At the moment what we have is PWA and WASM and icons on the desktop.
At least for stuff that doesn't use device API's much, it seems like websites are the way to go. They're a whole lot easier to build than mobile apps.
I think we already have plenty of avenue in ‘solutions’ like Electron to let people build bad apps.
The boring answer from Capt. Obvious. Incentive alignment.
That said, WebAssembly might be the trojan horse. While it started as a browser compile target, WebAssembly System Interface (WASI) is extending it beyond browsers into filesystem, networking, etc. etc. etc.
Fingers crossed, we may get cross-platform standards by accident.