Forum Moderators: rogerd
I DO use calendars on a couple of sites where schedules are important - but not the "forum" sort. These are run with perl....
I find it difficult to get excited about maintaining calendar functionality so that members can see when others have birthdays. Maybe that would be fun in a very "touchy-feely" community, but I find the giant lists of "Today's Birthdays" on some forums an annoying waste of home page real estate and bandwidth.
I've found most forum-bundled calendars are not as robust as I'd like, so for a hard core events-centered site (say a dating service that has many events every day/week for members to sign up and attend) more robust features might be necessary.
Those are a couple of good examples of using a forum calendar to support a community. More generally, I suppose, any forum community with a "real world" component like meetups, conferences, special interest group meetings, or even planned chat sessions could benefit from a calendar.
With a forum that doesn't have anything to do with events or gatherings, I think deleting the calendar is fine. It's probably just more work than you need to keep the calendar up to date and censored.