User base which knows better will never become their user base, until their strategy changes. This also creates their market view.

Now, which one is the chicken and which one is the egg?

As a consultant, I ran into a LOT of people who preferred POP3 on their phones and non-main devices. They just wanted to have as little email on their phone as possible (which also gives you decent security if the phone is lost).

Combine this with the fact that Outlook is just terrible with IMAP, and I didn't find too many regular users who liked it.

Personally, I wouldn't use anything else, of course.

How does the choice of protocol determine if there is as little email on non-mail devices as possible? Also, I've seen people screw up POP3 configuration so the mail moves to the downloading device (because it gets deleted from the server after downloading, as they didn't choose the "leave mail on server" option). If your phone is continuously checking for and downloading mail, that less security in the event your phone is lost, because copies of your email potentially exist in multiple places. With POP3, everything is copied (or moved) and you don't get a choice to only download some messages (after looking at subject lines or sender names) and leave some messages on the server.

True, looking back I forgot to include the part where they obsessively delete each email from their device after reading it.

The "Leave Mail" option is very important as well, especially when they really just want to leave the mail on the server long enough to get it on multiple devices (especially their main desktop), but the server has absurd size caps.

It's often a case of their expectations having already been set by their history with POP3, so anything working different is not what they want.

Well they had remote access for a while but started charging for it. I stopped using that feature. I think it was only pop3 anyway.