Face it, you've tried at one time or another. Have you been successful? Well, since you're reading this, probably not. Why is Graal so addictive? Why can't we quit? Well actually, let me explain the psychological side of things and group the types of people/audience that Graal appeals to.
First off, Graal brings back memories from our childhood. Not just because it represents Zelda: A Link To The Past. But because a lot of role-played as children. Such as little girls and boys who used to play "house". Dress up, have their little treehouse, pretend to cook, be who they wanna be. It may not seem like it, but this plays an important role in many peoples reason for playing. Subconsciously, of course.
Second, Graal allows you to be independent. Your own person. Its not a roleplaying game where you choose from pre-made characters, you get to grow yourself, your social status, change your look, and even submit your very own looks to make it even more personal. Being independent, we feel in control and being in control is "possessing" something. Making Graal one of our possessions, very hard to let go of. It grows on you. Ask the old-timers.
Third, for Classic, there's not much change. But that gives people an adrenaline rush when there is change. For Era, there is constant change which keeps your blood pumping, which is essential for the fast-paced style of Era.
Conclusively, Graal is like FaceBook, interactive. There are real people, real-time interaction, real connections, real friendships, etc. This gives you an emotional connection, along with the possessive personality. You may be able to quit for some time, maybe months or years at a time, but everyone will come back to it eventually. Whether in their thoughts, memories or on their iDevices/PCs.
I once got arrested and rushed to the hospital (don't ask). I was in the waiting room with the police officer who happened to ask me what I did in my spare time. I told him I liked to play games, so he asked me what kind of games. I said "Graal" and he knew exactly what I meant, cause he too played Graal when he was younger. According to him, the dating and babies still existed back then...I hope for a better future at least.