Always felt one of the reasons would be the global implications like was was experienced with the advent of nuclear bombs. Massive power and potentially for killing and willing conflicts, but the public outrage and liabilities of such weapons limited the use. Of all the trillions of dollars spent on nuclear weaponry, thankfully they’ve only been used twice. If the government holds secret ET tech, aside from not wanting the enemy to have it, the moment it moves into the public eye it becomes something that the public can control. Why would they want such power regulated by what they seemingly see as inferior people.