How would you like me to prove it? The simple fact is anyone reasonably dedicated to getting weed can get it within a few hours, certainly no more than a day. It is incredibly prevalent in today’s society. Again, Amsterdam’s example says that use will go down if it is legal. The whole forbidden fruit theory.
Since pro pot people like to compare pot against alcohol then answer these questions: Did alcohol consumption go up or down during prohibition? Did alcohol consumption go up or down after prohibition ended?