Isn't it obvious? Because governments aren't good at management. There's no incentive or feedback loop. A company goes out of business if it's operationally a mess or doesn't deliver value. Not always but it's highly correlated. Governments face no pressure like this. Maybe mild pressure on the very local level. But when you get to the national level, orgs like the Pentagon misplace trillions of dollars with not so much of a protest.

https://en.wikipedia.org/wiki/Government_Accountability_Offi...

The irony in your example is the modern Pentagon is largely a collection of private companies.