Why won't NASA tell about aliens?

"it's really obvious NASA found aliens and other life forms" - okay, show us the evidence you have to prove it.
If you don't have evidence, then its just conjecture and rational people don't deal in conjecture.

At the moment... there's nothing to tell.

What makes you think they found them?

Because NASA is an aerospace engineering organization. They are not in the business of writing science-fiction.

They do. They keep telling us that those salt deposits on Ceres are "something else" (no doubt alluding to work of space boogiemen). They also try to mislead us into thinking that every exoplanet they discover is "another Earth" implying that it is populated by dickheads like us.

However their efforts are wasted except on folk like you who have been primed by the hysteria channel to believe any amount of nonsense.

What more do you want from them?

Cheers!

Making such declaration would make you look very good if you could prove it, but as long as any data is not full-proof, it could potentially backfire, making the usa look ridiculous.

That information is classified. Those aliens kicked the Apollo 18 astronaut's butts- that doesn't make the USA look good.