I was on board until I saw that those can't easily be opened from a local file. Seems like local access is one of the main use case for archival formats.

Agreed, I was thinking it's like asm.js where it can "backdoor pilot" [1] an interesting use case into the browser by making it already supported by default.

But not being able to "just" load the file into a browser locally seems to defeat a lot of the point.

[1] https://en.wikipedia.org/wiki/Television_pilot#Backdoor_pilo...