Why are kids so rude nowadays?

I and my siblings were brought to be polite all the time and say hi first to whomever is an elder to us. But nowadays I see kids don't bother opening their mouth to say a simple "hi". They think it's not important or they should be said hi first. I am appalled by the lack of mannerism and impolitness going around today. When I raise my kid, I will make sure they have manners and knows when to say hi or they will be called out on it!
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Could it be the western culture? I'm from Iran
Why are kids so rude nowadays?
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