Okay, so maybe not all exiting employees say “thank you for the opportunity” and “it was a difficult decision to leave these amazing people and this place”.
Maybe they don’t tell you at what point their devotion changed, they no longer think of the company as “amazing”, they started looking elsewhere and have recently been feeling stressed, because breaking up is so very hard to do………
Your company needs closure, so they can move forward.
No really, YOU need to know what happened.