Also, accurately reporting about an arbitrary source of downtime means you're smart enough to avoid the same sources of downtime.
Not that this can't have been an obvious reason (deleting all the servers in a datacenter or similarly trivial but severe) but it's likely impossible to ensure status page accuracy.
That only indicate the frontend of the service is up and potentially running. Being about to respond to ping and being able to serve HTTP request are two different things, and being able to serve HTTP request vs a fully functional website are two different things. Think about wrong SSL certification, wrong domain mapping between frontend/backend, broken JS/CSS etc.
Most outages aren't so obvious as this one, and any ping will fail intermittently (often because the ping agent has a failure.) Google definitely has loads of pings hitting Google Calendar in various ways. Exposing this monitoring to the public is not practical or really useful. (And would aid would-be attackers.)
> We're investigating reports of an issue with Google Calendar. We will provide more information shortly. The affected users are unable to access Google Calendar.
Wasn't there that time AWS had some outage, but the red-circle picture (for failure) was itself hosted on the unavailable AWS service, so their status page didn't show it as being unavailable? Or am I mis-remembering something/repeating an urban legend?
"We're investigating reports of an issue with Google Calendar. We will provide more information shortly. The affected users are unable to access Google Calendar."
And I'm not surprised, since actually reporting it as down has a lot of political blowback (not to mention contract blowback) within the company.