I couldn’t find anything but I did find this with Superman!
Here’s an article I found. I got some of my information crossed.
My only off hand guess as to why is that Star Wars was more of cash cow comparably speaking. I can’t recall the figures but in Empire of Dreams it was said that Fox’s profits after the release were the highest the studio had ever experienced. So they probably wanted to make sure nobody else could profit off it as they’d lose that money coming in.
That’s so funny. I can’t help but picture Dracula riding off to his laboratory on a motorcycle now. Haha