FWIW, Google Calendar does support CalDAV:

https://developers.google.com/google-apps/calendar/caldav/v2...

It also supports a richer API, for features that don't fit into CalDAV:

https://developers.google.com/google-apps/calendar/overview

While I tend to agree with what I think is your point, it's all well and good to say that there's a standard and one should use it (which I support, and have worked on many throughout my career), but standards aren't a panacea either, especially since many of best standards are ones that standardize a previously proprietary (but working!) design.

(No relationship with the calendar team, but I'm pretty sure they'll read this thread if you have comments for them.)