it also has to do with , and this is a little trivia for ya'll that the characters only say the ''Anti Gravity'' line one time. When they first pass throught it they will say it, however if you get another AG section later they wont they it anymore until the next race and so on.
Also has to do with the fact that MK8 voices, while terrible (i think we all can agree on this) , are very veeeeeeery quiet compared to MKWii and the way the game handles how the clips play is just bad.
In MKWii the voice in action would be cut short if for example the character hits someone with an item.
As in Rosalina saying ''Wooooooooo'' with a boost and if she hits someone and it still isn't over saying that long Woooooo then she will say her ''Nice'' quote , completely canceling the other sound.
In Mario Kart 8 , the oppossite happens. The sounds that the character makes when hitting someone are cancelled by any other sound.
Which, even if i know is kinda nitpicking, i really hate.