There’s been a long history of them, and an entire industry doing things like filtering attachments or rendering HTML emails in sandboxes.
I think the original poster made an attribution error: iMessage gets attacked because it’s popular. If it didn’t allow you to receive rich messages from anyone, people would switch to other apps which do and there’s a long history of those being exploitable, too. What makes iMessage special is that you can assume an iPhone user has it enabled without having to check whether they use WhatsApp, Telegram, Facebook Messenger, etc.
There have been! One was in Microsoft Outlook parsing email subject lines, so you had to do was recieve email in order to get hacked. And there was another one around when heartbleed was a thing that had to do with parsing of the DNS lookup and response of who the email was coming from.
