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Instead of the native format for e-mail archives? Supported by every MUA ever made? Not really, no.

How would that help 99.5% of their user base?

As it currently stands, it's still not user friendly.

making it even less is not helpful

You literally just open mbox files with Apple Mail.app, it's the easiest action that the (now long-established) WIMP user interface offers.

absolutely not