Seriously, I don't know why but that's all I see whenever I see them arguing, which is probably the opposite of what is happening. But seriously, it wouldn't be the first time where two rivals ended up together and frankly that is one of my all-time favorite cliches. Also, if you think about Yamraiha says that whenever she is in front of someone she is interested all she can talk about is magic, which happens to be all that she argues about with Sharrkan. She also said that she wouldn't forgive him if he lost in a battle, raising another flag. I just really like them together for reasons I don't really understand myself.