For one thing, when you read a book that someone else wrote, you have, for that brief time, a reader/writer relationship with the author. The writer controls a lot of things in that relationship, but not everything. For one thing, writers often have little say about the book's cover, including the blurb on the back. But, the writer certainly chooses the plot, the characters, and the setting. He (or she, but I am going to just say “he” because it's awkward to say anything else; English sucks when it comes to gender and pronouns) decides how much detail and exposition to include, what tense and person to tell the story in, and whose point of view to use. Plus, of course, there's that harder to define thing called style.
Once the reader starts reading, though, the author has to yield some control. Every reader comes to a story with his own unique perspective. Sometimes a dislike is general, as for those of us (like me!) who can't tolerate present tense novels. Sometimes a dislike is specific, as when the protagonist has the same unusual name as the kid who tormented you in sixth grade and you can't stand to read it. Every choice the author makes could cost him one or more readers.
But so what? There is nothing that every single person likes, not even chocolate. Trying to play it safe isn't a good way to produce a good read. And the neat thing about the author/reader relationship is that neither one owes the other anything. If I don't like present tense, then I don't have to read the book! And the author doesn't owe me anything, either. If he decides he wants to suddenly switch from first person to third half way through the book, he can; it's his book. Of course, if I don't like that kind of seismic shift, then I may never buy anything else by him, but again, this is a no-strings relationship.
On the other hand, the most successful authors are those who do establish a sort of contract with the reader, a level of consistency as to style, and a faithfulness to the genre, if there is one. I once read a mystery where the detective didn't solve the crime, and I was pissed as hell at the author. I don't mean the detective didn't arrest the murderer, I mean he wasn't even sure who it was. A lot of romance readers get incensed if a book doesn't have a happy ending, and some hard science fiction fans will get huffy if the science in a book doesn't hold up to scrutiny. If you write in a genre, you do need to think about what your readers expect and consider carefully whether or not you want to break that implied contract.
In fact, you could even say that not meeting your readers' expectations could lead them to break up with you. -)