Insert image of applauding character here, because that's about as good a run-down of fandom's approach to shipping and fic in general and to Clint/Coulson in particular as one could hope to find.

If canon interaction were so crucial to any fandom, I doubt we'd see the AUs we do.

A while back I noticed the big difference between fangirls and fanboys. I mean, I hate to generalize based on gender, so maybe it should be more in fangirl/fanboy-dominated space or something like that, but anyway...fanboys seem more invested in what physical actions a character took (can Superman beat the Hulk?), whereas fangirls seem more invested in the emotional actions of the character (what do you think Tony went through when he realized he went farther from Earth than any human being ever and slaughtered thousands, if not millions, of the second alien species to make contact with Earth?). It's not a hard-and-fast rule, but it's part of, I guess, what lends fic toward not needing to rely on the canon actions of characters so much as the characters themselves.

Also, y'know, in all the explanations I've ever given for Clint/Coulson, I've almost never actually brought up the most obvious of "uptight and bespoke with snarky and rugged." Silly me.