Some of us still use POP3.
More importantly with POP - you mail gets downloaded to your device and then that's it. It's yours, secure, for you to manage. With IMAP there's always the possibility of the ISPs server hiccuping and deleting mail off your machine that you thought you had safely downloaded.
I used to be a POP fanatic, mostly because I didn't like the idea of leaving copies on the server. But then, the NSA probably logs everything, so hey.
It might not be correct now but at one point the Electronic Communications Privacy Act stipulated that data left on a server for more than 180 days is considered to be abandoned and the government can easily and legally access it.