Replace "Google" with "your email provider". Even if there were many diverse email providers with significant adoption, the problem would remain. Unless you're

Replace "Google" with "your email provider". Even if there were many diverse email providers with significant adoption, the problem would remain. Unless you're using PGP (and -- critically -- the other people know how to use it as well), then your email is stored as plaintext on your email provider's email server (and the email provider of anyone you send the email to, as well as any forwarding agents that passed the email along).