IMHO, this information should be gathered well before exit, e.g. through regular 1-on-1's, but that's another discussion.
Close relative has received a terminal diagnosis
Believed their horrorscope
Got pregnant
Saved enough money to retire to Thailand
Spouse has had an affair with a co-worker (Trust aside this is still a good reason)
> They can get a better deal (non-monetary) elsewhere
Just won the lottery, close relative received terminal diagnosis, got pregnant, believed their horoscope, saved enough to retire - these are all cases where someone believes they can get more value for themselves by leaving their job.
Spouse has had an affair with a co-worker probably goes under "not happy with the culture"...
People who leave usually negociate or talk up before they leave. If you need the exit interview, then your management is seriously unable to hear. In which case the exit interview won't be acted upon anyway.