As has been pointed out more times than I can count, and not just by me, anything we write that is meant to be read constitutes an implied contract with the reader, whoever that reader might be. The reader agrees to read what we’ve written with an open mind, and in return, you agree not to waste their time. I say anything, because this applies to a legal document or a business letter just as much as it applies to a work of fiction. One distinction is, in fiction, you’re allowed to play with reader expectations, mostly because you’re allowed to do anything, even things you don’t yet have the skill to get away with. Even when you do have that skill, turning readers’ expectations on their heads and making them like it is a trick you can only pull now and then, for the obvious reason that, if you do it enough, then the readers’ expectations change and now they’ll be disappointed if you don’t try to lead them down the garden path. The contract remains the same but the assumptions informing that contract change all the time.