Another aspect is that the morality of stories would often seem questionable nowadays. I have a collection of fairy tales from around the world, and I remember trying reading some of it to my son. Randomly choosing some Indian story about husband pressured into deceiving a bear to work for free and then stealing some pears from the neighbor's garden. The bear was later serendipitously scared away by the the couple and received no reward for doing the chores (the bear didn't do anything bad to them). That whole story just got weirder at every turn. I was waiting until the end, I was hoping the author would make a sharp turn and rectify all the injustice, but it just ended with the perpetrators celebrating their ill-gained profits.
Well, this story is from a different culture, different time... but, I also have Beatrix Potter's collection of short stories for children (which is only some 50 years old and is definitely from the Anglo world), and uhm... I do struggle to explain some "turns of the tongue" used in these stories to my son. And it's not because I don't know what the author meant. It just makes me feel uncomfortable that the author thought that describing someone as fat was clearly intended to portray them as stupid. Or how whipping mischievous children was seen as a virtue, and that the character suggesting this be done to Ms. Muppets' kittens was the virtuous one, whereas Ms. Muppets was a lousy parent (for failing to do so) in author's opinion.
I'm still against editing the old books, but I'm also against using them in the same capacity as they were originally intended. I'd rather have them as historical artefact presented with modern commentary.