I think, they still prefer to use that type of cameras for you to learn, how to take a perfect shot with just your skills and not by how great your camera is…
We know that non digital cameras had some problems when it comes to focus, blurring and lighting adjustments. It is just one of the things may be the school wants you to learn with. Once that you know how to do it with your old cams, it is much easier for you to do it with the digital cams.
Plus, not all people can afford to buy a digital cameras, so what if you are stucked in the country where the price of the cameras is too much, what would you do?
Lastly, the beauty of the picture in fine arts is not just judged by the way it looks… It is how the photographer made it a masterpiece and that is by his own skills.