Not sure about the vomiting as I see that extremely rarely in any of my fandoms, but drinking and smoking... w00t! it's the 70's everyone drinks and smokes to excess.
I don't know much of what you refer to in your post because I never watched SPN or Buffy but it seems many writers use it as a shortcut to actual inter character communication and relationship build up. Why write 10,000 words of back and forth backchat when you can get them to the point with drunken excess in under 500?
Some of it does have a point, like you say, in showing self loathing or masculine bravado.