why is weed such an avaliable drug to teens and why do we use it so much?

why has weed been such a effective drug for all teenagers to get hold of and smoke. this drug is to easy to be out like this that u can come and get it as easy as talking.as a teen i know how iis cause plenty of people have offered it and tried to cell it to me.some of our biggest drug dealers are not older than 20.