Because taxpayers aren’t paying for the private employees,
What you are missing is that the assignments are very minimal because they have way too many workers among whom to divide the work.
Again, taxpayers aren’t paying for cheating.
I worked for the govt for one year. Couldn’t stand all the make-work chores and just hanging around with the other workers because there wasn’t enough work. Left for corporate, and that was cut-throat: they expected 12 hours a day. Found a nice mid-point with non-profits: enough work, used my talents, but decent work-life balance.