While the xkcd comic mentions 14-15 competing standards, there are only 3 email client standards in wide use: POP/SMTP, IMAP/SMTP, and Microsoft Exchange ActiveSync. POP is wholly surpassed by IMAP in functionality and ActiveSync is proprietary, so we're left with IMAP/SMTP as the only viable universal option.
I would really like to see an open email client standard that is more reliable and performant than IMAP/SMTP, and JMAP could potentially be it. It doesn't seem unreasonable to have 2 competing standards instead of 1 when IMAP hasn't seen any improvements in 20 years.
POP3 is perfect for people like me that download their mail and organize it in local folders on their computer. I'm using Thunderbird and mail filters to move messages to their folder. I backup remotely with duplicity.
I check my mail with k9 on Android, delete uninteresting messages and download on my laptop, maybe only once every two or three days. To reply and send from Android and not to lose my message I configure k9 to Bcc me. I get my message in my mailbox and my filters on Thunderbird will put it into the right folder when I eventually download mail.
Of course I'm missing the ability to read my past mail from my phone but life has proven that it's not important neither for my work nor for private matters. Furthermore communications are moving more and more to WhatsApp and Telegram and those are always available on multiple devices.
I do have a Gmail account because of Android and maybe I self squatted a Gmail account before I had an Android phone. I can't remember.
However I have a POP3 mailbox bundled with a domain I own since last century. That's my personal email. I never moved it to Gmail because I always downloaded my mail: some emacs package, then Netscape, then Outlook express, then Thunderbird. As a software developer I'm always close to my laptop and before smartphones it was normal not to access email when we were on vacation or on weekends, holidays, etc. When I'm on vacation now I read my mail on my phone, reply and bcc me, leave all messages on the server and download them when I'm back home.
My work email is managed in the same way. Another POP3 account bundled with my own work domain name. No friend or customer ever complained about anything in almost 20 years, hence constant access to the archive of past email is a nice to have feature but not an important one.
well the other nice benefit is that since JMAP operates by talking JSON via HTTP over TLS you get to skip a lot of the absolutely bonkers annoying cert stuff, SMTP port issues, etc.
I would really like to see an open email client standard that is more reliable and performant than IMAP/SMTP, and JMAP could potentially be it. It doesn't seem unreasonable to have 2 competing standards instead of 1 when IMAP hasn't seen any improvements in 20 years.