I’m not talking about romances, here (that’s a whole different ball game), but other genres.
Personally I don’t think it does. In fact, many of the books which have stuck in my mind, and that I remember well, have had unusual or unorthodox endings. Gone Girl, for instance - the ending was definitely not what I was expecting, but I think it was totally appropriate for the story (although there are many readers who disagree with me).
Gone with the Wind is another. All the way through the book I was anticipating Scarlett and Rhett’s HEA, and it never happened, and I think the story was that much better, and more memorable, for it.
Possibly the most famous love story in the world, Romeo and Juliet(and yes, I know it’s not a novel), has a tragic ending, and the play would be a dismal affair if it was anything else.
Perhaps it’s not the lack of HEA, but the unexpectedness of it, that is the key. And sometimes the technique of leaving future events to the imagination of the reader is a powerful one. It also leaves the story open to a sequel, but that’s another story (excuse the dreadful pun!). As been as I’ve deviated from books, I may as well go the whole hog and bring other media into the argument. The Sopranos – it couldn’t have ended any other way. Leaving it to the viewer to decide is pure genius.
On the flip side – Gravity. What a waste of an ending. How much more powerful would it have been if Sandra Bullock had died on re-entry- or is that just my dark side peeking through?