Because then when you call in from the field with the reason as to why you refuse to go live during a thunderstorm, the ND having been a photog will know exactly what you are talking about and overrule the desk who is saying that you have enough time to get the shot out. Having a former photog as an ND or asst. ND or on the assignment desk just makes life all around easier because they know what you're facing because they faced the exact same thing when they were shooting and they know what the limitations are in the field.