Because they work for the government. Every agency does not have its own fleet of vehicles, especially those who would infrequently need them. A trip from Idaho to Texas would qualify as official government travel, probably at least a three day trip. The inspectors would have an authorized government card to pay for a rental car (as opposed to having to use their own car) and hotel rooms and a per diem to purchase food, fuel, etc. They would be incentivized to save money to get a cheaper hotel room. The curious part is not that they got a rental car. It’s that they decided to leave such sensitive stuff in the parking lot. I don’t even leave fishing poles in my car when traveling. I can’t imagine leaving nuclear material in the backseat. That is worse than leaving a gun in the car. The article didn’t say but I hope these inspectors were fired or severely punished.