Earlier quoted context omitted.
And I don't care if my browser is compromised, since the attacker would only get access to an empty VM on Qubes OS.
I'm not switching my os to some obscure one for security and it doesn't make sense for me to isolate my browser from my system/files. 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.