Its not just the US Govt but all powerful Govt i dont see why they cant tell the truth.

So noone knows why govts lie then?

Probably because most of them don't know the truth.

Could be but they can always learn ya know

They could but they are too busy skimming money off into their back pockets and secret bank accounts to bother with anything as mundane as the truth or even doing their jobs.

Too busy doing their best to get re-elected so they don't have to work for a living.

Actually I think I'll become a politician sounds like a real easy life.

How does the Right Wing Communists Party or
Left Wing Fascists Party sound?

And the answer is...............money.

They do so because it's very difficult for the "public" to find out the truth. Since they are the ones "making up" the truths.
And because of "National Security"