Hmm, now that you bring attention to it, I guess they did swear a lot for a movie at the time. I never really paid much attention. There were a few people around me who cursed like sailors so it fell on deaf ears to me.
But I think sometimes being around it you pick it up too unintentionally. Especially, when they're used as adjectives for everyday use. 
For me it was the problem of autism and parroting what you hear. Yeah. It took me years to flush that mostly out of my vocabulary. And just to be clear it wasn't my parents who cursed, it was the older teenage boys that hung out with my big bro. So I think younger kids in any age will follow what the older kids they look up to are doing.
Or you just pick up the vernacular if you hear it enough.
_________________
In my darkest hour I reached for a hand and found a paw.
"I sat with my anger long enough, until she told me her real name was grief."