Why would anyone pick POP, other than as a poor-man's SMTP replacement for picking up mail off some other server and dumping it into another IMAP or other server-side mailbox system?
1. I use Gmail apps for business, but unlike many people, I don't like the Gmail UI. I use a desktop client most of the time.
2. With Gmail + pop, I always have access to my email, but I can also make localized backups from my desktop client.
3. I don't trust that Gmail will retain my data forever or that I would never lose access to my account. I'm not paranoid about Google, but ultimately it's my responsibility to backup my mail data, not theirs.
If I recall correctly, moving an IMAP email message into a local directory that the IMAP account didn't know about deleted it from the server, which I did not want. But I had this huge local organizational structure for all my emails from multiple accounts, so I could either choose to exclude Gmail from this organization, reconfigure everything so that my brand-new, unproven Gmail account was the master account that controlled everything, or just turn on Gmail's POP mode and maintain the status quo.
Honest question: If I have multiple email accounts, some of which are IMAP and some of which are POP, that I organize with a mail client on my local machine into directories that mix mail from all the accounts (is it even possible?), then if I change the directory structure on the server of one of the IMAP accounts, what is supposed to happen to my local directory structure and all the non-IMAP-mail or IMAP-mail-from-other-accounts, that used to be in those directories?