Have you ever noticed the number of couples who break up, one of them uses the lets just be friends speech, and then they never talk again?
I mean that speech is really just code for "lets never see each other ever again".
So why bother using it?
To let them down easy?
The real reason is because the person doing the breakup speech is too gutless to tell the truth.
It is in essence a sign of a person who is too immature to tell the truth and is still stuck in a highschool dating mindframe where they would be seeing the other person at school regularly and thus would want to maintain a friendly relationship for appearances sake and to prevent possible complications / hateful rumours.
But if a person isn't in highschool any more then it is time to start telling the truth. Tell them why you are breaking up with them.
Eg. I want someone who looks different.
I want to meet someone who is more like me.
I like dating badboys who treat me like crap and you're too nice to be a badboy.