I was big into GinHiji when I started reading/watching it. Then, during the underground fighting ring episode, when Sougo mentioned he'd help Kagura with committing seppuku, and Kagura replied, 'oh, he definitely likes me', I started paying attention to them then, and I suppose my liking of them overruled GinHiji by a landslide. Apparently, they're the second most popular Gintama pairing. The Gintama DVD site had a poll or something, where you got to choose your favorite pairing to be on the cover, and they got second. Majorly proud of that.
No prizes as to guessing which pairing came first.