There is a small locally owned fast food outfit here in Anchorage that still makes fries from spuds - you can watch them prepare and cook the food, they WANT you to see what you are getting.
The fries (and shakes) are the best, they use homemade ice cream for the shakes.
Another reason to spend the summer in Alaska I guess.
In Ocean City Maryland there is a stand on the Boardwalk called Thrashers. They too use real potatoes and they cook them in peanut oil. No trip to Ocean City is without a stop there to get some fires. Like you say they do it all right there in front of you. They have a long line of people waiting.
But McDonalds and others seem to think they can fool the public with a poor substitute.
Ease of preparation probably has a lot to do with it. Its pretty easy to dump a batch of prepared fake frozen potatoes into some grease and hit the start button.
I am pretty sure with McDonalds they cant hire someone for minimum wage smart enough to cook a real potato. I dont go there often but last time I did they dont even wait for the fires to take on a Golden hue they get them out as soon as they start turning yellow. Half cooked.