That's true, but sometimes I think it works better in some cases than others. A good example would be Peanuts. For the most part, the comics and the strips went together. They both had the same spirit, and both were Charles Schulz's vision. And he must have had a lot of love for his comic. Even as he grew older and his hand wasn't as steady as it used to be, he still drew his comic. He could have retired long before he did and lived comfortably, but he kept working on his comic and that, to me, is nothing short of an inspiration.
On the other hand, I look at Garfield and while I loved the old cartoons and the comic strips, the newer movies and things just haven't complemented the franchise as well. And the fact that there are many ghost artists for the strip makes it... well, less personal to me. It's not that having ghost writers and ghost artists isn't uncommon, especially in successful comics. It just feels very corporate.
Even with The Wizard of Oz, it is a little sad to know that the film is very little like the book.