This is one of the mysterious absurdities of human world. Humans subject themselves and their children to brainwashing due to an error in judgment.
Generally humans do certain actions because
Humans believe the actions are good for them or others.
Not acting may cause harm to self or others.
These actions feel good now or later. (Humans are much dependent on delayed gratification.) Not acting may cause punishment now or later. (Humans are fear much delayed punishment.) Negative actions are sometimes done by some people because they believe these actions feel good.
Peer pressure
Copying others
Inertia
Sometimes, experimentation
Sometimes, desire of harm, suicidal tendency.
Most of these reasons apply to perpetuation of brainwashing. Much of the brainwashing is done by inertia, not by choice. People are taught to brainwash themselves and follow what they have been taught.
Majority of humans are very limited in their ability to think independently. Part of this limitation is upbringing. Upbringing, especially in poor countries is directed to save the society from harm and much effort is put in standardizing the students and making them harmless to the society.
Peer pressure and copying others is a huge factor in brainwashing. People often feel ashamed when they are caught by peers not to be knowledgeable about the news and modern trends. The subject of news is a typical topic of conversations between humans. This is especially irrational because of the fact that most news are artificially fabricated by the establishment (which is controlled by MIC). Many of the events sold by the establishment as news are preplanned and theatrically performed. Independent thinkers are aware of that and read the news "between the lines". That is, independent thinkers are capable of seeing the deception in the news and understand the true meaning of the events behind the news.
MIC = military-industrial complex