People smoke marijuana out of pleasure, that's pretty much it. I know that most are generally introduced to it out of peer pressure, but they don't stick at it because they developed some sort of addiction, nor do they experience physical withdrawal upon quitting. It's just a matter of endlessly experiencing that "high" feeling. To answer your question, no. I didn't need any rehab for quitting marijuana, I simply quit and never looked back. That's probably the best thing about marijuana: you can quit whenever you want to, haha.