Can old people not use mousepads?
Re the effect of calloused finger tips caused by metal guitar strings does this account for the fact that when I tried to teach an old friend to use a laptop she couldn't make the cursor move although I could? Does this mean that with an ageing population computer designers may have to produce more sensitive touch pads geared to the changed skin in older finger tips?
As you age, your skin tends to get thinner, so it's unlikely to be the same effect as with the guitar string callouses. In fact, thinner skin should be picked up more easily by the trackpad system. Obviously, it depend on your life history - maybe your mature friend is a thrash metal guitarist?