Maybe that manager moves to another org that you want to apply at, and they reject you because of how you acted the last time

Good, I don’t have to work with them again, win for me

Doing this has zero benefits to you

Catharsis comes to mind, on top of the schadenfreude

sending an email takes almost zero effort

Yeah, and thats part of why not doing it sends a point

If your workers hate working for you so much they won’t even send an email then you should evaluate your management and work culture, yakno?