Even the big authors make mistakes

I've read and heard several complaints about how self-published books are filled with grammar mistakes and more. Having just finished reading Stephen King's Mile 81, it seems that even the big authors make  mistakes. This boggles me actually. Where was his editor on this one? How could someone of his caliber put something out to the public with such glaring mistakes? I counted at least seven and the book, according to my Nook, is only 52 pages long. Now, just because he made those errors, it doesn't make it okay. I still strive to do the very best I can every day. It's a battle, I tell you. BUT, it does make me feel a tad bit better knowing that the best have flaws too. After all, he is human. His stories freak me out, but he is still human.