What is the cultural/sociological explanation for why Americans assume so much in daily conversation?

Is it the motto "manifest destiny"? Is it class blindness/the wage gap? Is it mass denial of a health crisis? Ethnocentricity?

I often hear things like "you must be married," "you must be single," "you must not get laid" (???), "you must be a dude," or "you must be desperate" over trivial things. It's odd because when I hear or read things like this, there's often little to no basis for it. Other countries make these jokes too, but there's usually some basis. When Americans do it, it often feels like the only basis is "I hate you," making it more of an attack than a joke. I also see smaller assumptions, like "you want a coffee" or "you're out for the day." It gets tiring after a while.