I've always assumed most Cangel fans fell in love with the idea of the pairing, before it became explicit in the text. I love the idea of them. I didn't need it to happen, but I would have been there for it if it did. By season 3, their chemistry was so well established that any group of machine typing monkeys could have written a better love story for them than what we actually saw.
For me it began already before it started in the series in season one around the time after IWRY and post Doyle.