Dumb Question?

I am afraid that I have what is probably a dumb question, however I hope that there be someone here to maybe anser anyway. I am very new to 3-d graficks, and perhaps do not understand some premise of it yet, so please forgiv me. I have seen here from time to time people asking for models of products that are in existence. I have seen it here at least 10 times in the past year. There is a gentlemen here who asks for a model of a Military Truck. This gentlemen is a very fine one, and popular on this group, and I believe he is professional desiner. This truck is allready in production, which I know, because I have seen in my country, in conflict. My dumb question is this, and I ask with no disrespect do I Intend for the gentlmen of who asks for the model. I have to assume that being a professional desiner, he will be paid for his work from this large company who produces this truck. Why would the company pay for a model of a truck when there must be enormus amount of photograps available to this truck. Secondly when it was first designed and produced, they most certanly had to have desiners make renderings of the truck at first. I guess the question is why when something is in existence, does it need another model? With utmost respect, Marcos