A pay freeze
for federal workers is the sort of gimmicky deficit reduction measure that you could see using as a bargaining chip in broader negotiations over how to best reduce the deficit. But as a standalone, unilateral concession? It doesn't do much to actually reduce the deficit and it's a shot at a core part of the Democratic base, so why concede it right off the bat?
The DLC-esque Third Way
offers its explanation: "The President's announcement today recognizes that we need to take serious action to get the deficit under control, and that we need to take a 'government goes first' approach to build public trust and prepare for the sacrifices we'll need to put our fiscal house in order."
"Government goes first" usually means "Democrats go first" in these negotiations. Republicans then use that concession to redefine the "middle" as further to the right -- at which point Democrats concede again and the whole cycle repeats itself.