On the other hand, sometimes I wonder if my friends' parents weren't a lot wilder than I used to think.
I'd bet. I always thought that my extended family (parents, uncles, aunts, some of their friends) were honest, square and boring people whose wildest times consisted in only one beer more than appropriate every now and then, and staying out longer than their parent's had allowed.
How wrong I was. They were a young and wild bunch. And I learned some pretty "undescent" things about my oh-so-strongly-catholic aunt.
I bet some of them actually had sex, for instance.
(Not mine, though, of course. 
)
Of course, lol. I'm sure I was brought to earth from the strork too
But my experience is that people who didn't grow up using drugs as teenagers are somewhat unlikely to start using them as they approach 40,
I know some parents from friends who tried their first pot when they were in their fifties. Their children (then in their thirties) were tired of lying and hiding to their parents and finally told their parents that they were smoking pot for ages. Some of the parents were eager to try it themselves
But sure it's more unlikely than start using drugs in ones teenage years.
Back to Ennis and Jack:
I still think it fits somehow. In the 70s, when smoking dope became popular, they were between 26 and 36. More around thirty than around forty years.
Jack came around a lot. And he was in general more boyish, playful, more of a dreamer, more of a risk-taker, more open to having fun in various forms and more willing to trespass given rules (shooting a sheep, for example) than Ennis was. More open in many ways. So I can picture him being open to try something new, something that promises to be fun.
And
Mexico is a good argument from delalluvia.
