I think the difficulty of getting any federal position has a lot to do with it. I can't say how many people have told me that I'm incredibly lucky to have been offered a position in a mere 5 months, and I probably never would have gotten a federal job if it hadn't been for my Peace Corps service. Now, agencies are further cutting back on new hires. Meanwhile, if someone in private industry really wants you they are capable of making a decision within a month or so. Government may provide job security in the long run, but it's very insecure while you're waiting to see if you've made it past one of the many obstacles in the process.