Also, "public" here means only the time & title, not detailed description, participants, attachments etc. You can easily set individual events to private, or default everything to private if you wish.

It's ultimately the individual employee that knows whether or not a meeting is relevant to them. And they can only know that if they have information on the meeting.

Sounds like an entirely toxic environment.

Proper etiquette would be to ping the meeting organizer and ask if they mind if you sit in. If they don't, no problem. If they do, you work something out relevant to the reason you wanted to sit in. But one can't even start that conversation without knowledge of relevant meeting topics.

The fact I know what meetings my coworkers are having doesn't imply I should be crashing them any more than the fact I can see when my coworkers are at their desks implies I should be continuously bothering them.

Google's corporate culture is to make it as easy as possible to have that happen.