I see lots of people do things that are commonly written off as rude too. I don't know if there is much of a monoculture around what's rude or not, if people do

I see lots of people do things that are commonly written off as rude too. I don't know if there is much of a monoculture around what's rude or not, if people don't care (then is it truly rude?), or maybe the writings like this are simply outdated.