Transparency makes work more efficient for others. That's why I keep my calendar events public by default.
Anyone can see what meetings I'm attending, and should they need to double book a time slot, they have more context about my schedule than "Busy".
Some events are more flexible than others for rescheduling. One-on-ones can be easily rescheduled (never canceled!). The same is true for standups or other meetings with my directs. Availability becomes trickier the higher up the org chart the attendee list is.
What about confidential events? I'm skilled enough to maintain my own calendar and will make those meetings "private" on a case-by-case basis.