Probably because it would be difficult to show book pages on TV without it looking warped due to curved pages (or that the images were too small). So, they simply created larger versions of the art. Also keep in mind that they had a 15 minute limit per episode.
This is not the original telling of the book. It is a bit disappointing and leaves out some great literary components of the story.
My guess would be they couldn't fit it all into 15 minutes. I think the point is to get kids to read the stories for themselves.
Probably because it would be difficult to show book pages on TV without it looking warped due to curved pages (or that the images were too small). So, they simply created larger versions of the art. Also keep in mind that they had a 15 minute limit per episode.