It's not even about age.
You can twist an ankle playing basketball and need accessibility features like ramps and grab bars.
You can get hit in the eye by a bit of debris when your toy drone crashes, and need help reading a screen while it heals.
People who don't think they need accessibility only have to wait. Everyone gets their turn.
Bad analogy, as none of those traits require any accomodation in a website or app.
Not that I disagree with the premise. Almost everyone will eventually have trouble reading small, low contrast text or details on their phone or screen, if nothing else.