Sorry but I have to agree it is not particularly an age thing. Though distance will obviously play a role.
We've brought our children up in the country their grandmothers were both born, but a long distance from where they are/were and where we grew up. So both had the "been there done that" understanding of what it is like to have babies and young children without your mother around to help. And in some practical ways the world is so much smaller than it used to be, albeit covid has put some of the size back!
We've had a couple of occasions in particular where my mother dropped everything to come and help - once when my eldest was sick and in hospital, I remember it didn't feel quite so properly serious until my mother asked me on the phone, should I come over?, and after pausing a moment I realised the answer was, yes please. Later she ceased her self-employed teaching and came and stayed with me for most of two years so I could finish postgrad work while she helped with the house and children, school runs etc.
We are in a transition phase at the moment, as she is now in her 80s and trying to downsize, not so well anymore and it will be good when she is closer to us being able to give her a hand in return at last. But she still cares ++ - only the other day she instigated a serious conversation with me about just how she could help me get my weight problems sorted out, as she has pointed out before we have family history of overweight people with heart problems from their 50s, and I'm not far off that age now :(
Having said all of that, there are different ways of showing you care, and with the world's changes some are more difficult or seem less worth pursuing than they used to be. Also, some mothers perhaps feel it is most important to allow you to have your own family - maybe your mother had a bad experience of her own mother or mil trying to control and dominate how she brought you up, and wants to keep things at arms length.
I hope you can forge a new form of your relationship that works for you.
(I've also just remembered when I was first learning about proverbs. My mother told me that "distance makes the heart grow fonder" and "out of sight out of mind" were good descriptions of my two grandmothers respectively ...)