We only arrest a very small fraction of people who break the speed limit, yet you wouldn't suggest that speed limits are BS.
I've explained this to you before: Speed limits, stop signs and the like are intended for orderly traffic flow. Operating a motor vehicle poses a degree of risk to other drivers. Violating traffic laws is a non-consensual crime. Violating traffic laws poses a threat to other drivers -- the threat of initiating force and willful negligence toward the safety of other drivers and pedestrians. Drug possession doesn't pose a threat to anyone nor does drug dealing or private drug use. They are consensual crimes -- no threat of force or willful negligence toward the safety of other persons.
That's arguable, but let's skip it. Who says drug possession must pose a threat to others before it can be regulated? Not our constitution, that's for sure.
As a matter of fact, you can't name one society or one government throughout history that limited their laws only to behavior that posed a threat to others.
So, where did you get your "threat" standard? Just making it up?