Oh you were Navy, now it all makes sense
This really is the whole point. I had to handle classified emails at a time when the technology was still relatively new and there were no established protocols. Yet even as a rank and file peon, I knew not to throw my then AOL email account into the mix. This was before mobile devices, which meant a lot of late nights sitting around monitoring an email account on a secure system. Convenience never factored into my thinking. It did for Clinton.
Diligence around classification levels was of paramount importance despite the admitted tendency to over classify everything.