Because, as others have pointed out, those events may not be things they wished to share.
Let's pretend you like activity X, and you'd like to keep that private. It could do with your sexual tastes. You may be a member of the Jarjar Binks fan-club. It doesn't matter, as long as it's something you'd prefer not everyone to know.
Let's say you also have a trusted friend who also likes X, and they invite you to an event. Except that event is marked as a public event (as determined by the event creator, not by you). You may decline the event, or not even respond to the invitation, and this may have even been years ago. However you're still in the event_member table, and that can still be retrieved by applications.
The end result is it's possible for friends to reveal your personal and private interests by inviting you to public events. Unless you take care to weed these out, those interests can then be found and inferred in the future.
The good news is that if you remove the event from your calendar entirely, then you're also removed from the event_member table, but I still have to test that fully.
As a general rule, sharing events information with your friends' applications is probably a bad idea, but luckily this can be turned off. I don't believe there's a way to prevent them being shared with applications you've voluntarily installed.
Let's pretend you like activity X, and you'd like to keep that private. It could do with your sexual tastes. You may be a member of the Jarjar Binks fan-club. It doesn't matter, as long as it's something you'd prefer not everyone to know.
Let's say you also have a trusted friend who also likes X, and they invite you to an event. Except that event is marked as a public event (as determined by the event creator, not by you). You may decline the event, or not even respond to the invitation, and this may have even been years ago. However you're still in the event_member table, and that can still be retrieved by applications.
The end result is it's possible for friends to reveal your personal and private interests by inviting you to public events. Unless you take care to weed these out, those interests can then be found and inferred in the future.
The good news is that if you remove the event from your calendar entirely, then you're also removed from the event_member table, but I still have to test that fully.
As a general rule, sharing events information with your friends' applications is probably a bad idea, but luckily this can be turned off. I don't believe there's a way to prevent them being shared with applications you've voluntarily installed.