Agreed. Not necessary to cup feed. More natural NOT to cup feed.
But cup/bowl feeding is sometimes helfpul / expedient, so it doesnt hurt to get the chameleon used to the idea.
Cup feeding allows you to count how much is eaten in a given amount of time, without having to be there watching.
Cup feeding, once the chameleon has associated the cup with food, helps you when introducing a new prey item easilly.
Cup feeding can contain things like roaches or crickets, which you wouldnt want escaping into your house if uneaten, or left to potentially nibble on a sleeping chameleon.
Bugs kept in a cup waiting for their demise can themselves be kept fed more easily (and thus be kept more nutritious) than free-ranged prey.