In some calendar I import into my main calendar, e.g. importing AirBnB to a central calendar, I don't want to display all info of the event as it's private (the name of the person that rent a flat). I think an option to "privatise" event and just label it "Busy" instead of the event title would be perfect.
We don't have any plans to combine private and public events in a single calendar for now. But you have had requests for private calendars, altogether.