Because there's no easy way of asking your parents whether she's still with us without letting on that you can't even be bothered to keep track of who's dead in the family and who isn’t..
"Mum, just a quickie. Vis-à-vis Auntie Min… What a lady! Formidable, in many ways… Er. Now then. Would it be fair to say… What I'm really driving at here is… OK, I'm just going to put this out there -- is she still alive? … Ah that's brilliant. Honestly, I'm made up for her."
(No but seriously mum, is she or not? Because I really can't remember.)