They're rarely completely mandatory (Grandma still needs to be able to access her bank too), but the alternative is usually a whole lot more inconvenient (sometimes for bad reasons, sometimes just because that's how life is).

> (Grandma still needs to be able to access her bank too)

In some countries they are mandated if not by law then by implementation, a relative or a social worker is tasked to get grandma equipped with a "smart device". She can even borrow it for a few months from municipality services until she can afford to buy it