Why Chad and Karin? They only had like one scene together and it wasn't even romantic. So.. what gives?
Sometimes just one scene can be enough for your imagination to go wild actually! Obviously their canon interaction wasn’t romantic in the slightest, but what interests me — and I suppose the other few shippers?— is the myriad of possibilities that can happen afterwards. I consider their encounter as “shipping basis”, if you want. Since they still are linked by Ichigo and their spiritual powers, it is likely that one day, they will meet again, when both are grown ups and have developped the powers they gained in each other’s presence. (Now that Bleach is reaching its end, it seems doomed, but when the chapter with Karin going to Urahara’s came out, I was dying to see her joining her brother’s gang with some awesome Shinigami / Fullbringer powers, and teaming up with Chad again… *quiet sobs*) (it really seemed possible at the time)
Anyway, I think their first encounter can be regarded as very symbolical, since it’s a turning point in their both of their lives, and they go through it together : they are suddenly forced to mature, to acknowledge the world of the deads, deal with new powers and responsabilities. Even if that doesn’t become love afterwards, you can’t remain indifferent to somebody with whom you shared such an intense and life-changing experience. In my opinion.
Furthermore, what I really, really like, is the chemistry they had, at that moment, as partners. If I keep analysing their characters and tempers, with always the idea that they’ll meet again older, I found out that they had the kind of potential relationship I appreciate in a pairing. Very different but complementary and balanced personalities, a renewed chemestry, but to a whole new level. I assumed that their differences would bring out the best in the other, and also reveal what no one else could, because I felt that they both had very different way of dealing with their emotions, but probably a common understanding, regarding of their respective lives. However, I am aware that as in any ship, it is very subjective indeed, and a lot of people might not see what I see there. It’s just that to me, it is the quality content I am looking for in a pairing.
So technically, yes, in the canon material, there is nothing to go crazy about. It is a shipping about if, purely about what could happen. However, I think it’s the reason behind every crack pairing, and I’m kind of sad to see this one particularly raises scepticism. Just to take example of Karin, she is mostly paired with Toshiro (whom she canonically never met, so well), but I’ve also heard people shipping her with Grimmjow, or Aizen? And like nobody bats an eye? And I’m only quoting examples involving her, but god knows there are a ton of others, and if I’m okay with them, I just don’t understand why specifically Chad and Karin can be so surpring, after all I’ve seen in this fandom. At least, they had a scene together…Anyway! I am very sorry for the long answer, but believe me, I tried to make it as short as I could. I was considering to make a whole post dedicated to all the reasons that make them a good pairing, so maybe it’s about time… I nonetheless hope this answer was satisfying! Do not hesitate to drop any other question :)