A need is not a convenience.
This isn’t accurate. [Perhaps you misconstrued what ‘Knowledge-bomb’ mentioned also.]
A need can be a convenience, look at it like a geriatric male/female scenario, where maybe they want the fall detection capability, so they obviously need it, but it also is a convenience if they have the ability to use the watch in a situation where it can alert someone if they don’t have someone monitoring them. Need and convenience are mutually exclusive, maybe your definition is just skewed.