Um, is there an echo in here?

I have heard time and time again that one of the biggest things agents and editors look for in your work is a "unique voice."  Everyone wants it.  Everyone strives for it.  But my recent reading seems contradictory to this advice.  During my binge-reading these past few months, I have read four books with practically the same voice.  I won't say what books they are or who wrote them, but I will say they are all contemporary novels written, agented, and edited by different people.  This "echoed" voice is that of the quirky, snarky, klutzy, foot-in-mouth, counter-culture, teenage rebel girl. 

Honestly, I don't read a lot of contemporary YA fiction, so perhaps this is the norm for the genre.  But it seems strange to me that four books with four first-person female narrators sound so darn alike.  Don't get me wrong, I have thoroughly enjoyed each of these novels.  Their storylines were completely different and engaging--it's just that over the span of my reading, the separate voices all blended into one not-so-unique voice.  As I currently read the fourth book with this "echo" voice, I find myself groaning inwardly and thinking, "I get it--she's the Queen of Wit.  Yes, she inevitably embarrasses herself in front of the boy she likes.  Of course she says the worst thing possible to her <insert authority figure here>.  Yeah, she curses like a sailor even though she's not supposed to--what a bleeping rebel."  And don't forget that beneath that hard, crusty exterior there's inevitably a gooey nougat center of feelings.  It just gets a little tedious to break through that shell after a while.  Snark, snark, snark.  Angst, angst, angst.  Snarkity, snark, angst, snarky. 

To me, this matter raises a lot of questions.  Has the snarky, teenage voice now become overdone?  Are all these books written this way because it is in fact the modern teen voice--the one most teens relate to?  (I can't imagine EVERY teen in the world registers a 10 on the Sassy Scale.)  Is this voice something to emulate or avoid, then?  Arguably, this suggests that now the "unique" voice would be that of the quiet, studious teen who thinks before she speaks and does not step out of line.  Boring, perhaps, but unique nonetheless.  Am I just horribly out of touch with my former sixteen year old self?  Completely nuts?  Is it a fluke occurrence that I happened to pick up four books with coincidentally similar voices?  Maybe writers and avid readers of the genre would read these same books and point out a billion ways in which the voices are different.  Maybe they would read the fantasy I favor and say, "You're daft.  These books sound all the same to me!"  Or is it really the plots that made these four books stand out in the sea of hopeful manuscripts, masquerading as a unique voice?  Perhaps voice really isn't as pivotal as everyone makes it sound, but rather a piece of the whole.  I just don't know.  But it's something to ponder, don't you think?