Because whatever savings it creates are, as Tom said, minor and highly debatable. Remember that freezing pay isn't just a matter of dollars and cents; you do that long enough and your best young talent will leave the civilian sector to work for private contractors, who will charge the government significantly more for that person's knowledge and skill sets. On the other hand we spend RIDICULOUS amounts of money on pet weapons and systems projects that are years and hundreds of millions of dollars behind schedule. You want to squeeze the DoD budget in a substantial way? Make commands justify every line item of their budget and provide harsh accountability for overbudget and overschedule projects.

I'm telling you from first-hand knowledge that the potential there is MUCH better than 2%.