Pencils are pretty simple in how they work - a bit of graphite that leaes a mark when you rub it on paper. But that bit of graphite can vary quite a lot, and there are a lot of different ways of holding it. Wrap it in wood, grip it with a clutch mechanism, or even add a clicky mechanism to extend more lead with the push of a button. All have their advantages, their fans, and their uses.
Nothing beats the simplicity of a wood-cased pencil, and they are very flexible in the marks they can make. But a mechanical pencil stays sharp, and only needs a click instead of sharpening. And a clutch pencil can be a nice compromise when you want thicker lead without the wood.