I have wondered this exact same thing. Actually, my wife and I were discussing my addiction and I said "it will calm down once I hit max level". She then asked what that was and I told her Level 30...so maybe its just the completionist gamer in me that says "I want to beat this game and see all that it has to offer." This game is fun, but not when it takes so much grinding. However, if it weren't so grindy, we would probably be done with the limited content Bungie has provided at launch within the 3 weeks or so we have already played it, and all just playing PVP. The lottery/rng aspect has people hooked...and when all it takes to get a new lottery ticket (engram, xur money, raid loot) is a few hours of repetitive gameplay, we are all for it.

I've been struggling with the same question for myself. Do I really enjoy playing Destiny or am I just obsessed with leveling my character? I have to say doing the same missions over and over again is getting boring. However, I do enjoy the crucible. Sometimes I feel I'm just endlessly trying to level up my character so I won't get left behind. I've been gaming for a while and I don't usually play MMO's so this is definitely a new experience for me. I'm usually playing Battlefield where I enjoy the game and can put it down for a while and come back and pick up right where I left off but with Destiny I feel like if I don't play it every day I'll be missing out on some reward that I don't know. Very weird.