Governments are keen on keeping EVERYTHING secret.
Just to list some:
-Area 51 a.k.a. 'Dreamland'
-The Roswell Incident
-The More Recent 50 ft. perimeter surrounding the Pentagon
-Alien spacecraft crusing around the Moon
-Any Alien Abductions
It only seems prudent that they would still deny other types of aliens even though we know of their existance.
Oh, trust me, I am aware of that happening today....though from experience on the forum, people don't like hearing about them, they tend to get hostile.
And why Starfleet, of all folks, would still adhere to a Brookings style policy? Bad enough they got a Prime Directive, now it seems self imposed.
And look where Starfleet wound up, loosing 40 ships and crew to the Borg. Why would Starfleet keep secret stuff? Treating citizens and personal like children never has positive results, be it in our world or the Trek world. I hold to the idea that Starfleet's personally responsible for the deaths and destruction the Borg caused in their early appearances. And I think some pretty harsh punishments should be dealt to the ones who decided to keep it secret and to the ones who enforced them and kept the cloak and dagger mentality going. And it's supposed to be the people and citizens who control the government, not vice versa, though most folks would probably get bent out of shape at that concept.
^ Well, for one thing, governments and military organizations are fond of their secrets. On top of that, I'm sure there are a number of security implications surrounding whatever advanced technology was found/retrieved. In our own era, we don't exactly leave important weapons or energy schematics laying around for anybody to access, so why would Starfleet / UESPA?
Yea, and look at the hell our world is in today with that system. I think we'd probably have a much more advanced world, publicly, if it were the other way around.