Right!
But all the pieces are in place. A windows laptop can easily push messages to my phone, technically.
And through that, my mail-client could send a message to my phone "here's an ical, handle it in the appropriate app" if it finds ical info in the email.
Hell, my web-browser could recognize semantic markup like https://schema.org/Event to add a button or context menu "put in my calendar" if it finds an event.
Everything is in place, designed, discussed, finetuned, re-done, redone again.
and now abandoned because non of the big players have incentives to use and push this forward in their browsers (Google), OS (microsoft, Apple, Android), suites and so on, because that would increase interoperability and thus make it easier for users to switch to a competitor.
