I know many baby-boomer friends and relatives who smoke weed.
They smoked when young, as part of their culture. They gave it up (or reduced it a lot) during family-formation and professional working years.
They have taken up smoking weed again in retirement. I attribute as an attempt to return to the carefree days of their youth, especially since their responsibilities are now lessened. As for health/cognitive effects - the attitude seems to be “screw it, I’ll do what I want, and I’m getting old anyway”
Pretty good psychologizing... I agree with most of it. That was a pattern I saw many times with my generation.