options>general>confirmation>raid invite It says: Toggle whether you want to receive raid invite confirmation window. Somehow it toggled itself off. I was getting raid invites and not seeing them, so I was not accepting them. Why would anyone not want to see their raid invites?
Alts, 'friends and family', 'retired', etc - those who don't raid and don't want to be bothered when the raid leader invites everybody. Although I agree that it's completely unnecessary. Non-raid characters can always click No or just ignore the invite and let it go away. It's not like raid invites happen often anyway.
It used to be widely used in the days of old when open raids were every hour almost. Some of the smaller guilds would use it to get enough players to join a raid to make the raid happen. A lot of time we did not want to see raid invites if we were pledges or too low on the pole to attend and sometimes certain raid leaders would just invite everyone all the time. Just like the translocation to bind or guild hall that goes out to the entire zone is not wanted by everyone but that also used to be widely used. I think I was the last one to cast that in lobby yesterday. But those translocate's used to come in every half hour ! Random raid invites, translocation spells, guild invites, those mana wands and many other all inclusive stuff used to be much more common. Like the LFG (looking for group tool) that no one uses anymore.
