I'm just not trusting a small browser dev team.
The risk of exploits is too high
The risk of exploits is too high
Random exploits on the Internet are still a higher risk for me.
And yes my mail account is more critical than my local files.
I open my email in a dedicated VM, so only my email provider could attempt to compromise me. Attachments are automatically opened in another, disposable VM.
Also my email account and everything normal I do, is part of my normal life and it's very helpful to be normal.
If I would ever do something out of the ordinary and want to do something which requires physical access, it's much easier to travel the world as someone who has a normal Internet profile.
My personal data is protected enough on Gmail and gdrive.
Everything else just doesn't exist anywhere.