We "all" feel the same way? Speak for yourself. Personally I find this obsession with slideshows a bit odd. If any of them ever appear again it'll be retconned anyway, and if they don't, I'd rather just use my imagination.
Any sort of epilogue scenes or slides need not be written in such a way as to require heavy retconning in the event that one of the characters returns though. Think of it as a sort of setting the stage for potential future events/stories for the character. They may not want to go so far as to completely lay out all the events of a given character's life after the end of the game for that reason, yet they could still give the player a general idea of where they might be or end up if there were a "Baldur's Gate 4" or expansion on the horizon. Epilogues can also serve as a nice wrap up and recap of everything you as the player managed to accomplish in your own playthrough.
