Why do some parents not show support or affection towards their children ? Is it because they grew up that way?

I'd say that's accurate a lot of the time. My dad was verbally and physically abusive towards me when I was a child and very emotionally distant, probably because he grew up in a household where that was normal.

My mother believed there were chosen children and slave children. Either you were chosen for training by her cult group (a generational political cult located inside the old CPUSA), or you were to be subdued and fully controlled, mainly through the use of fear, and were to be an unknowing slave, serving the revolution though ignorant of your subservient role. Lack of affection was a standard part of raising a slave child.

I don't know about all parents.
Mine never showed support or affection after my mom passed. From then on, everything changed. I was four, my brother one. He always seemed so bitter. Nevwr was abusive, but more like he didn't care.

Not everyone has a maternal/paternal instinct. It is a myth every mother has one.
Some people are just not cut out to be parents. And some, just too broken.

My parents raised five kids and their minds were on providing a roof over our heads and food in our bellies.

I have heard that excuse. Break the cycle.

They don't comprehend the importance of their position! People don't pay attention to anything, and self honesty is completely lacking. The reason you put forth is just an excuse in my opinion. Parents should be willing to make exceptions for their own children, each generation is supposed to be an improvement upon the last.

My grandmother was mean and hateful, her sisters and brother were not quite as bad. I believe so.

actually yes,same as abuse,it's what they know,

That would be my guess. They never learned how to express affection so it feels awkward for them. Lacking the ability to at least be supportive though is a shame..words of support or a physical presence of support goes a long way.

I believe so...😔

majority....