But any time you stop using a hard drive you should clean it. I have probably 6 hard drives on a shelf in my house because I've replaced them with larger or faster drives. Each one has had the free space randomized twice and then set to all zeros afterward. Bank info, taxes, official (unclassified) work files, all of those have been on them in some variety at some points, and if they are ever disposed, I don't want any of that to be easily recoverable. I have never used it to destroy evidence when it was requested by investigators, as I am not a wealthy and powerful person, I would end up incriminating myself by doing so.
This was my thought as well. I will say up front that I don't like Hillary and I think she's unquestionably guilty of mishandling classified information, but I think it's entirely within the realm of reason that her server was wiped as a matter of standard procedure vs something more nefarious. I wouldn't put it past her to have it wiped to prevent anything she doesn't want us to know, but I would hope that anyone involved in government IT wipes drive as a matter of SOP.