Why do champs with literally 7 lines for attacking/moving have unused voice over?

Title, when the warwick line of him getting banned got leaked everyone thought it was his new visual update. A ritoer then said its just unfiltered voice over from a unused line. Thing that bothered me is why do characters that old have unused voice over that could be easily put in their movement so we dont get repeat vo, like nunu can say "Lets make tracks!" 2-3 times in a row if you get unlucky enough. Sorry if i dont make sense this just made me upset and confused