I can understand not shipping Sterek (and definitely expecting them to have more scenes together; as big as the pairing is you'd think they were interacting every episode) however (at least in my opinion), they are far from a crackship. Derek doesn't spend a ton of time with any of the characters on the show other than Scott and Peter, so I don't see why shipping him with Stiles is more far fetched than shipping him with most anyone else. They have a rapport, people like that. They've also grown from simply annoying each other to respecting and trusting one another (even a little fondness, there), so their relationship has made some progress. Plus, Derek does care about Stiles' safety, and even when he didn't even like the kid he still protected him. It might not mean "Derek is in love, omg" (in actuality it says more about what kind of person Derek is, but the point still stands), but it's something people can build off of in fanfiction.

*shrugs*