WHY DO PEOPLE GET OLDER?

Its not that I'm asking a very irrelevant question, I'm pretty sure you have answers to this, its just that an old women, at about her 70's I guess, asked me this question while I was riding a bus on the way to Baguio City that it took me a minute or so to answer her in return. c",

Shocked and a bit petrified because I was unexpected and I thought it was euphoric question. I told her that people gets older because they choose to lived, not much of a sense I guess because she smacked a grin smile, realization maybe of how shallow I am to her or maybe thst she know what I would say and its just a node of confirmation, expected, but anyhow it bothered me which lead to the creation of this post.

Being in a medical profession, I should have told her that it was due to our body composition and that our body progress and retard due to chemical interaction within our natural state of reciprocity against the world around us but I didn't and I couldn't. What I told her is a choice to lived as if its our sole choice canceling human natures biologic interrelation. But how, what and in which way will I simplify the answer to adapt to her thoughts, a 70+ year old, wise woman?

I was thinking rather that she despise her current condition, white pearly hairs. weak body, grunt skin, that she questions the very essence of life's cycle and that she wish to have been younger yet wiser,. I wish I could comfort her with such remorse but there is really nothing she can do with it no matter how many question she will asked or how witty she might be. She will retard and rest in God's time and that she should just be happy about it.

Maybe she wants to tell me something rather, that I should cherish my life while I'm still young, that I should live my life to the fullest, do things that my heart desire, conjure to the best that life can offer before its to late, a bit to late for her...

...If you were asked with the same question, what will be your answer?