Names and story titles are a sensitive area in every writer's anatomy. You can critique a story's grammar, characters, plot, and pacing to your heart's desire, and most authors will listen patiently. Some will even take your suggestions to heart. But the moment you tell a writer that his/her story title doesn't work for you, or that the protagonist's name was unpronounceable, or that s/he should've named the planet something other than Fizbal, they lose interest in your critique.
It's not that changing the name would be difficult--computerized search and replace has made that argument obsolete. It's not that they spent enormous amounts of time and effort devising their names--if they did, you wouldn't have spotted the flaws so easily. True, renaming someone might upset their mental image of the character, but even this could be finessed by holding off the search/replace until the last minute. I think the real problem is that everyone thinks s/he's an expert at naming.
How many parents seek expert help naming their babies? No, consulting a book doesn't count. I mean, how many would be willing to hand off the final decision to an expert? Now think how many kids hate the names their parents stuck them with.
Think about the thousands of people who contribute to naming contests, confident that they have the perfect name for the newest microprocessor chip or consumer product.
When it comes to naming, most people assume they are extraordinarily clever-- infallible, even. So when you criticize someone's choice of names, you cut their ego to the core.
I'm reminded of the primeval couple in Mark Twain's "Eve's Diary" and "Extracts from Adam's Diary." Eve says that Adam "can't think of a rational name to save him" while he fumes that her way of naming things is "mere waywardness and imbecility."