[..] the arms trade isn’t really about directly protecting national security. The arms trade is about the transfer of arms from the US, Europe, and Russia to the developing world in exchange for cash, in a process that can empower dictators, fuel wars, and facilitate human rights abuses.
Guns kill people. So too do tanks and bombs.
The business of buying weapons that takes place in the Pentagon is a corrupt business - ethically and morally corrupt from top to bottom. The process is dominated by advocacy, with few, if any, checks and balances. Most people in power like this system of doing business and do not want it changed.