What do you say when someone asks "How's Mum"?

Why do people ask this question? It really irritates me and you are right when you try and answer they just glaze over.
What you feel like saying is "if your that interested,get your backside over to see her!!" but of course we don't. Am with Barb on this one! But being me,I wouldn't dream of saying anything of the sort.
I usually say,she will never get any better but she is safe and settled and thats the most we can ask for. A usual nodding of the head comes in reply and tell your mum I was asking after her and i nod and thats that!
Love Lisa.xx