Because it's the one film that EVERYONE keeps bringing up. Fortunately I've seen the TV version (where Borat segments are interspersed with Ali G clips) and fortunately I've talked to Laura K. Thus, I was able to say something reasonably intelligent about Borat in class today.
..and my two cents to the discussion is this: I think Borat makes audiences uncomfortable because he blurs the distinction between script and reality. We've had Christopher Guest mockumentaries. We've had TV newsreporter "interviews with idiots in the park." But the former are clearly operating under the "it's all a script" code and the latter fall neatly under "it's reality, and these people are just dumb" code. But Borat and Ali G are characters (scripted) while their interviewees are not (reality). The behind-the-scenes manufacture is not as evident to the audience. Conflicting codes are at operation.
At least, this is how I first reacted. I couldn't tell if these people were dumb and sincere. Or scriptedly dumb. There is a different way to react to either interpretation (the laughing at/laughing with syndrome). And so I didn't know how to react. And I could feel how uncomfortable some of the interviewees were because they didn't know how to react. Their uncomfortableness further fed mine. What the heck was going on? I wondered. When I found out more about Borat, I suddenly found it more funny, because it suddenly seemed more manageable. I finally knew what I was laughing at.
Borat...is like a club. Because when Borat laughs...it is like when a club laughs. And when Borat crys....it is like when a club, how do you say it, cries. And when Borat is hungry....it is like when the club is hungry....
....and when Borat is sleepy, it is like when the club is sleepy...
.....and when Borat needs a lift, it is like when a club needs a lift...
...and when Borat is exclusive, it is like when a club is exclusive...
....and when Borat buys expensive jewelry, it is like....when a club buys expensive jewelry...
...and so that is why in Sarah's mind, we say that Borat is like a club.
And that whole parody will be funny to no one but those who have seen the particular "a man is like a horse" episode.