It depends on how you define "being installed". All files living on FileAPI and IndexedDB does not make too much difference than using direct file access and SQLite. They will be cached and they will live on your computer. Well, at least until your browser faces storage pressure and decides to randomly delete website data.
I mean, yeah, everything lives in a sandbox and there's potentially less security issues. Not having to give admin privileges to an application which allows you to build houses out of blocks is a good idea. On the other hand, the capabilities of the platform is increasing like crazy and it's just a matter of time before it converges with the operating system itself.
So, I don't know. The whole situation is weird. I think we needed better operating systems with granular permissions and we're getting there using a very convoluted way.
Precisely. It's sandboxed. I very much like the idea that I could run any proprietary software inside a sandbox, and reserve "hard install" to FOSS.
Also, I just can't ignore the convenience factor.
WebAssembly has the potential to say play video games, including AAA titles, without having to install anything on your computer. Same goes for many software projects such as CAD, office, video editing... You could use all this from your browser.
I don't know about you, but I find this perspective very exciting.