I can vouch for 420 workouts. Maybe it's not for everyone, but for me, there are some pretty clear benefits.
First and most obviously, my chronic back and joint pain is less intense, allowing for a more pleasurable workout.
Secondly, getting in the zone and not overthinking my activity allows me to flow creatively through new routines. Mixing it up promotes muscle confusion and leads to increased muscle density.
Third, I feel a stronger connection with my mind, body and spirit. I'm more focused on my breathing and technique, putting stress on my muscles, and not on my joints and my mind. I don't always smoke when I work out, but I've noticed if I go a long time without it, my technique gets really poor and I realize I'm putting myself at risk for injury. One 420 session and I'm able to correct my alignment, posture, and rhythm and it seems to reset me for future exercises.
Fourth, my mental and physical endurance increases.
Fifth, my sex drive increases, which definitely counts as a workout.