Lil I'd much rather they not reply than to send me an 'I'm not interested' email

Really? I think a reply ties up lose ends. Makes it easier to know what "is" going on, rather than guessing.

I know some people pick apart reasons or defended points, so maybe someone doesn't want to go through that so they sort of melt to the back ground.

At one place where I work, I liked the exit interviews. Good chance to see another side of the departing employee and to hear some things that wouldn't be normally said. Some diss’ing and some growth for me statements, in almost all exit interviews. Some exit interviews were all about the person leaving. That was good too.

Lou