It's probably impossible to implement due to memory shortage. Most things are buffered once they've been used once. Animations, effects, and even sounds. Having to load more at once would most likely crash consoles.
FFXI has been re-using the same sound effects for the past 8 years. And this is also exactly how other games work in general. All Weapon(skill) hits (blunt/slashing/piercing being diffirent sounds) and all the magic of the same element uses the exact same sound. The only diffirence that can be heard is in a pitch or in the duration of the sound, along with the fade. It's the exact same sound file however so things dont need to be loaded for no good reason. Fire-ey woosh of Fire and the long woosh of Firaga? Same thing. Your first slash, and your slightly higher pitched slash following that? Same file, diffirent pitch/speed.
Bard songs especially are a reasonable example. The complete bard song is about 16 seconds long, however the only times you will hear the finish is if you lag out or if you are extremely Addled. otherwise only a portion of the song can be heard each time. Threnodies finish in a second or two. Buffs take 8 seconds to cast most of the time. It's not exactly the same, but most sound and effect files are a little longer, and are then applied on spells and effects as pieces. Fire 1 uses 0.5 seconds of the file, a firaga would play 2 seconds of the file at a diffirent pitch.
You may say, but it's only one additional sound. That's true. But you'd be amazed at how small the buffer is that can be used for games, as well as how close they are on filling it all the time. That's why coding things for the xbox is such a pain, and also why console users have to relog after every Voidwatch, Campaign Battle, Assault or Besieged (if they even make it through).
It's to clear the buffer from filling up and freezing the console.