I think it became socially acceptable because there’s not a huge reason to hate on it.

The risks to cognition and health exist, but they’re no where near as bad as alcohol or cigarettes (and the negative effects basically don’t exist at low, even moderate doses)

The biggest negative effect of using weed regularly is it seems to slowly kill people’s motivation to do stuff over time. It will turn just about anyone into a couch potato. That’s more dangerous than any other effect IMO.