Not a product manager but I habitually try to play devil's advocate as one. I think it's popularity, full stop. You _could_ vibe code a native app no problem - but then you're targeting one set of hardware. If you're already just vibing it, why not make something that will work cross-platform while you're at it? And if an LLM is prompted with that, they'll usually go with the popular choice: web app on Electron.
Okay, but Windows isn't cross-platform.
Adobe is but they have a ginormous multi-decade codebase that mastered cross-platform UI ages, an LLM coding assistant ought to be able to "add a range input here using our standard UI library" much more easily than "rebuild this with Electron."
1Password at least has a decent excuse for a rotten decision.
There are plenty of cross platform options. I write with Qt for example.