For most consumers POP3 neither meets their requirements nor their expectations.
Most people consume their email not only from their single PC but also from smart phones, tablets and webmail.
And they expect to see the same INBOX (and message history and folders) on all those devices.
In the past most of not all pop3 clients defaulted to automatically delete messages from the server after successful download. (I don’t know if that is still the case for all but I assume that is still the case for many POP3 clients.)
So if you had checked your mail on your PC any new messages would be downloaded there and those messages won’t be visible nor available in webmail or on your smartphone.
To protect users from accidentally configuring a single device to use POP3 and subsequently having to field complaints that their inbox is now empty on all their other devices, a provider has very valid reasons to not enable POP3 at all.
(And yes POP3 clients usually have a hidden / advanced option to NOT delete messages after successful download but people only re-discover that option after all messages have been deleted from the server.
And IIRC POP3 only allows messages to be downloaded and/or deleted from a mailserver, but there is no upload. A user can’t copy messages back from their email client to the server. )
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With IMAP and MAPI the expectations and defaults are to store the messages serverside and you get a complete mailbox regardless of which method you use check your email.
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So IMHO as a provider you don’t encourage users to use POP3 because it does not meet their expectations and it makes quite a lot of sense to disable the POP3 service even when your software supports it. It is a legacy protocol.
Even though from the perspective of the provider pop3 is ideal because when the majority of your users regularly check their e-mail, download any new messages and delete everything from the server, you only need a fraction of the storage compared to users storing all mail on the server.