I think in Stargate the general population of Earth never knew that Stargates and aliens existed.
So I get that the idea behind the show is that there is a secret operation that most humans don't know about. And, at the beginning, it makes some sense.
Although I haven't seen all the episodes I remember several where many earthlings actually know about the "truth". With all the other outposts, teams, star ships, etc. and incidents happening, there must be thousands of people who know. It seems highly unlikely that this information doesn't leak. There's even a story arc about leaking information.
So, because it is one idea of the writers, the characters think they shouldn't tell Earth. I get that.
But why did the writers think so? Is there any reason for this?
They let them visit many planets where everyone knows and nothing bad comes out of it. And it seems later in the show, they try to wind around the fact that it doesn't make much sense to not tell humanity and it actually seems that half of them know already.
So why not just let Earth know? I even think this would have created great new possibilities for the show. Like how does Earth cope with knowing, civilian exploration teams, aliens on Earth interacting with people, and so on.
So why did the writers never consider that?