IMHO, there are two uses for dissonance:
1) to retain the listener's attention
2) to prove a philosophical point

the first point is evident in a lot of Beatles chord progressions where they borrow chords from other keys to mix things up.

the second point is mostly used by jazz and classical composers where they use dissonance to move to another segment of the song, or to move the original idea to a darker or even lighter aspect, etc

my favourite usage of dissonance is the ambiguity we hear in "the girl from ipanema". It's hard to solo to that chord progression unless you totally let go and just imagine yourself at the beach or something since there's not a lot to hold on to because of the changes in key.

I write about singing and voice techniques in my singing blog