Why is cannabis not sold by it's effects in the US?

[methMADMAN]

Swim used to notice (back when swim smoked) that different weed had vastly different effects. Swim liked the kind that motivated him to do projects or have great sex. But swim also got a lot that mostly blasted swim out of swim's skull and made swim a couch potato or rendered swim too sleepy to go on with swim's day. If swim still smoked swim would much prefer if different strains were sold according to their effects much like swim has heard of in places like Amsterdam (Lovely city too bad swim was 14 and had the parent ball and chain when swim visited). Why the heck doesn't American sources do this?