So, I smoked weed as a kid in the 90's and have kids now. What you say seems logical but in fact is just preposterously wrong. It is far, far easier for kids to get weed now. I'm California, Oregon at least, it's everywhere. Everywhere. Y kid finds discarded pens with plenty of THC left lying on the ground where teenagers hang out. It's damn near impossible to avoid.
I also supported and support legalization. But don't fool yourself. In states where it's legal-recreational, weed is everywhere from middle school on up. And with the pens it's harder to know if your kid is using it.
Our kid had depression and anxiety and it's an issue we are dealing with at 13. Personally, based on what I know now, I would recommend every parent test randomly once in a while for the combo nicotine and weed tests. Even if you think there's no way. Don't make it emotional. Just let them know it's a thing that will happen from time to time so that they can tell friends "oh my parents suck, they don't trust me, ill get caught if I try it. " It gives them another tool to resist peer pressure if nothing else. But we live in a very affluent, high expectation neighborhood in Northern California and in middle school the rate of kids who have tried weed is over 60% easily. Easily. My kid thinks its closer to 80%. I know for sure some kids are regular users and their parents would never imagine.