Because Harry has never shown any romantic interest in Hermione... ou vice versa...? They clearly have a brother-sister relationship. That is why Harmione weirds me out.
Ron and Hermione however, have always had (well at least from the third book on ward) a sexual tension between one another. That and the fact that they're freaking adorable.
It is because Ron and Hermione sort of have this romance that even if fans would l’amour Harry and Hermione would stick together forever,they don't have the chemistry.
Yeah i agree with the last person. Harry & hermione are sweet together but there is absolutely NO SPARK between them-it is just like they are brother & sister. Now she is very close with Ron too but not quite as close because of that sexual chemistry. For some reason even though she met them both at the same age, she bonds with harry as plus of a brother. It's like they get along INSTANTLY. Ron expressed dislike for her in the beginning, but thier love/like for each other has grown plus & plus over the years. That adds up to plus chemistry. In my opinion.