People question why the heck anyone would bother with pop3 in 2023. At Mailsac we find people still use pop3 for testing delivery. It is unsophisticated. Most people use our json to fetch the mail, but sometimes they’ve already got an smtp library open and use the pop feature.
The pop protocol is so simple it’s a fun toy to write, as well. You can do pop against most mail providers. It’s not very secure of course. But has value as a learning tool, too. Knowing how to write text parsers is a useful CS skill.