Because it is a bi-partisan scandal. HRC is not the first or the only high placed government official who has exercised complete control over her what-should-be-public-communications, she is simply the latest.
The George W. Bush White House under Karl Rove, Scott Walker and Jeb Bush have all utilized private email servers while in office and they were subject to either state or Federal transparency, open records and sunshine laws. Mitt Romney's staff purchased hard drives and wiped the server of all email records of his administration. So far they have all suffered no bad consequences or prosecutions or any ill effects aside from the hand wringing of people who naively believe in government transparency and/or accountability or in trying to recreate an accurate historical record while also putting a damper on rampant corruption and self-serving behavior.
Since the use of private servers is apparently an accepted practice among all the smartest and wiliest politicos, this current scandal will go nowhere. Someone on the current Benghazi commission will realize that at some time in the hopefully not too distant future, they too might have need of a private server - in fact why has it taken them so long to realize that this is status quo among the elites already?
While this ability to flout open records law and FOIA requests SHOULD be illegal and SHOULD be a scandal, it will not be.
Our journalists, such as they are, and our media will tell us, as always, that "no laws were broken" or if they were, they have been broken successfully in the past, so why worry now and isn't that sort of unfair in the grand scheme of things anyway? And isn't that really what matters most, that we turn a bi-partisan blind eye to the peccadilloes and minor or major crimes of TPTB so as not to be unduly upset about that which we have no ability to change anyway?