Because they're in power. I recommend Jacques Ellul's
Propaganda. The fact that the tactics are totally obvious is, in fact,
exactly the point. They serve not to convince, but
remind who has the power.
Ellul has a passage in which ancient Chinese poetry is "analyzed" by communist party members. This was served in classrooms of course. And the analysis was manifestly ridiculous. Anyone who reads it can't help but chuckle at the ham-fisted attempt to suggest that a poem about the sky, actually was referring to the glorious peoples revolution.
But: read that every day, hear in class every year, hear 1000 messages that confirm and reinforce this crazy, idiotic, message, and you can't help but be affected by it.
That is the nature of propaganda. In it's essence, it is a demonstration, an exercise of power. There is nothing subtle about it, and only part of it is covert.