LOL, shipping. the only instance in this universe where "but they look so pretty together!" is a politically correct argument.
perhaps not very convincing and/or valid, but...
as far as K/A goes, though, i don't particularly think it's "prominent"
it seems like a rather small niche, actually. it's just that eva monkey-sama and tines-san are sort of omnipresent around here, so it seems that way ;) people do ship it though, for varied reasons...
1. the aforementioned "they look pretty together!" or "hot," or "sexy," or any variation of it (they do look pretty together, IMO. i don't ship them but i have to admit they have some gorgeous fanart
2. people think Shinji/Asuka would cause the world to implode and just to be contrary they decide to root for a pairing that seems even more contrary, in an "i'd ship anything
before shipping S/A!" way.
3. people actually like
the fact that the pairing seems to be rather contrary. opposites attract and all that?
personally, like i said above i don't ship them. i don't care much for kaworu and if i have to pair Asuka with anyone other than Shinji, i prefer kensuke or touji. aaaaand i generally can't imagine their direct interactions as anything other than kaworu finding it tremendously entertaining to psychoanalyze her and Asuka finding it tremendously entertaining to think of all the ways she can punch/slap/kick that annoying smile off his face...
however, i think it could be an interesting possibility given the fact that they have so much going against them. it's a challenge: you know, if one can write a decent fanfic where it seems at least plausible that they could end up together, it would be a major triumph for the author. @legendary--
haha, thanks for that digimon flashback! aahhh, those were the days. it was such a complicated fandom to ship in
it was the one case where i was completely sure my main ship wouldn't
ever happen in canon... and then it did.
lol, sometimes i think the TOEI people were bigger trolls than anno himself.