I used to be a bank auditor and would audit for compliance with the bank’s policies and procedures. One of the primary reasons for having policies and procedures is to make sure that you are in compliance with applicable laws. By ignoring & circumventing “the rules” as the media is reporting it, i.e. those policies & procedures to comply with FOIA & protect classified information, Hilly has broken the laws themselves. As someone said “Email rules? Who knew there were ‘email rules’?” Again, those ‘email rules’ were there to make sure laws were not broken .... although the media is reporting more than they were prior to the IG’s report, the larger issue is being marginalized ... still.
The most likely reason is that the the emails contained discussions--even negotiations--about her sale of State Department favors for contributions to the Clinton Foundation. This HAD to be done on private servers so they could be destroyed if sought by Congress or the DOJ.
Even peons in the federal gov know there are email rules