OP, it's not as simple as you're thinking at all...only certain people employed within the federal government (or local government for that matter) are issued smart phones for official use. Most employees who are offered the phones are government workers who are in the field more often than in the office, otherwise they would be supplied with a desk phone.
Those who do get phones have a fairly set in stone regulation set that must be abided by in order to retain the phone. Private use of the phone is very much frowned upon, and the phones are usually locked out of general application purchases unless they are relevant to the work function of the employee (obviously people figure out work arounds for this, and use their work phone for private usage all the time, but the regulations are still there).
The phones are also property of the government, so one does not get to keep them...they can be recovered at any time, they can be wiped and locked down at any time, and have numerous monitoring applications running on them so the government knows exactly who, what and why you were using it at any given time.
I had an HTC EVO for quite some time before they started offering iPhones...switched to a 5 then a 5S before i resigned from my federal position. That phone was strictly used for official duty in my case because honestly, I didn't need the feds breathing down my neck for using it otherwise...I never even made so much as a personal phone call on the thing, especially with a perfectly functional personal iPhone that was with me at all times as well.