The thing is, at least for me personally. Yes, Ichigo and Rukia had/have great chemistry. But I couldn't really see them as a couple. I like the mentor/partnership/friendship they have going on, but anything further than that, I can't really imagine.
On the other hand Orihime and Ichigo is just incredibly bland and painfully boring. Disappointed Orihime got reduced to Ichigos trophy wife.
I mean for Fuck sake, she had better ''chemistry'' with that Ulquiorra guy. Their interaction with each other were much more interesting and entertaining to follow. Orihime actually did stand up to Ulquiorra and challenge his worldview. Ulquiorra also never saw Orihime as weak and he was fascinated by her since she was the complete opposite of him.
With Ichigo, Orihime just falls into the background and I never felt Ichigo really respected her the same way he did Rukia.