You don’t need a drug dealer for marijuana, you can grow in your backyard.
Two points.
1.A lot of people move on beyond marijuana. That's why it's considered a "gateway" drug. They will be eventually needing a dealer.
2. You can grow tobacco in your back yard too, but eventually someone from the government is going to show up and cause you grief. Perhaps that will be different for pot, but I shouldn't be surprised if they decide that only "authorized" pot can be grown.