Most people have addictive personalities...just to what is the question. :-) For some, it's substances. For others, it's behaviours. For others it's physical sensations (most commonly, sexual sensations). For others, it's emotional habits, like anger or worrying. When anything occupies more of a person's time, energy or money than it ought to, to the point where it is damaging some other important aspects of their life, it's an addiction.

Pot is just the teeny tip of the iceberg when it comes to addictions. It could just as well have remained a useful plant used to make rope, sails, clothing, and lubricants...but it got a cultural reputation as a mind-altering drug in the 20th century, and there you go.

People have a way of being really silly, given half a chance.