Don't forget that at the end of the 70s people were much more into wild experimentation and hedonistic adventures. There was not really a fear of sexual diseases like HIV or aids back then, all that came later.
POSSIBLE OPENERS AFTER YOU'VE GOTTEN DRUNK AND SLEPT IN YOUR GUY ROOMMATE'S BED (A LIST):1. Hey, Drew, thanks for letting me sleep in your bed. I hope I didn't puke all over your sheets. 2. What do you mean? I slept in your bed? Really? I don't remember any of it, I was so wasted. 3. Thanks for not trying to molest me.