Why Kili and Tauriel won't snog in The Hobbit

So I watched The Hobbit – the Desolation of Smaug over Easter – cosied up by the fire with a dog on my knee, wearing a beanie.  Yes, yes, I know, I know.  I said I wouldn’t watch it; said I hated The Hobbit .  But a few people told me to stop being so picky, so finickity, that I should forget about how it bears precious little resemblance to the book and that I should ignore the fact that it’s been stretched so far that its plot might snap into three overworked exhausted pieces. ...