At it’s most basic, I’d suggest, the answer is because he doesn’t have to.
Some background first, perhaps. Presumably as part of the publicity for his new novel, The Shining-sequel Doctor Sleep, Stephen King has given an interview to the BBC in which he explains why he doesn’t like Stanley Kubrick’s classic adaptation of his novel.
Now, I don’t think it was a secret that Mr King wasn’t a fan. Certainly it didn’t surprise me. But it seems to have kicked up a bit of an online storm, with the New Statesman posting a particularly smug piece entitled “Stephen King still won’t accept Kubrick’s genius“.