I'm confused by your post. If you carry a Superdrive as an extra accessory you still have it when you need it on the go. I don't understand why your posts suggests that external drives are mutually exclusive with using them on the go.
He's not saying that external drives are mutually exclusive with using them only on the go, he's basically saying (and I agree) that what's the point of buying a notebook without a superdrive, then buy an external superdrive, then take it with you on the go when you need it? If you have to take it with you, you're better off getting a Macbook with a built-in optical drive. It's more inconvenient to carry the external vs. having it built-in.