True, but Joe Dipseedoodle doesn't accidentally send out an HR report because he was logged into his personal email account.

Too much security is willing to give up on the 95% because they can't get the 100%.

For example corporations might want to make sure that worker is not sending e-mails with confidential data from its gmail. Sophisticated thief surely will circumvent that kind of protection, but a lot of thieves are stupid, so simple measures actually work.