– iCalendar (.ics) attachment can’t be added in Gmail app to Apple Calendar

.ics attached can be viewed in Gmail app, but there are no button to add it to Apple Calendar.

Gmail image:

In Mail app the window looks same but has buttons to add the event:

Also there is no option to share the attachment into the Calendar directly.
I see that Gmail app parsed the event info, but even with Google Calendar installed I can not do anything with it. I have these options in Gmail app on Android.

Why is that and is there another easy option to import this event without Apple Mail?
It’s Google who did not code this feature or Apple’s restriction?

Edit: no answer to “why”.