Not to mention the power they have and the terror they can inspire from being all Gestapo when it comes to a simple plant. They are funded by those who know what their profit margins would do if that useful plant was allowed to be legal. So, they fight it like spoiled little children who don't want to share their toys. Hell, I am surprised that Ohio has not created a special task force that is parked along the MI border and waits for people to drive back after being there for only a few hours. They have already created target data so that they can figure out which cars might have cannabis in them, as all law enforcement did back in the day.
Fun Fact: The tests they use for alcohol detects the amount in your system. Which is fine since one cannot be drunk without having drank the alcohol. The same with cocaine. If it is in your system, you are under the infuence. Cannabis also has this type of test. The main difference (and why they don't want to lose this cash cow) is that cannabis can be floating around in your system for 30 days or more depending on your frequency of ingestion. However, the effects only last a few hours depending on your metabolism. So, they have a test that can detect the residue but there is no way to determine whether or not you are actually under the effects. That becomes their opinion. It is grossly unfair and they know this. Which is why they do not want to lose this. It is a bonanza of cash over residue that may not even be affecting you at the time of the arrest. Until they create a test that can detect being affected by cannabis, there will always be an extreme bias towards keeping cannabis illegal since they know they can get you even if you are not actually 'high'.