I have no definitive answer.

My belief is that these records have gained in popularity, due in part to two main events over the last 12 years:

1) the focus on African American Genealogy and Civil War Pension File details (National Archives)
http://tinyurl.com/ogdlcu

2) the passage of the "Freedmen's Bureau Records Preservation Act of 2000". [Thanks Pearl Alice!]
http://www.afrigeneas.com/HR5157.html

Pension Packets were initially very affordable ($35.00 for the COMPLETE Soldier/Pension file). Unfortunately, the current cost has been a deterrent for many that consider them a 'risk'.

These files are a first-hand history lesson - especially if one expands the scope to neighbors, Unit members, deponents, and family pension files.

When these records are available in some 'digital' online repository, this broader value will be highlighted - helping us understand the COMMUNITY and their inter-connections in the Pre and Post Civil War era.