It has an addictive quality, I think it is related to the timers. You get to click on things and earn certain bonuses or items necessary to go click on other things. There are limits to these bonuses based on time, they replenish at a certain rate that is slower than you wish it was. You could opt to spend cash to get the items, and that's where they make money, or you can wait until they replenish automatically. The element of waiting/reward cycle is I think where the addictive pattern is centered, but it is easy to shake off when something new comes around to fill the time you used to spend moving your mouse around clicking on things. The difference in game over time is actually very little if anything, in order to make room for both the money spending players, and the non money spending players, other wise the players who spent money would totally dominate. As a result the games never really materially advance, there are just more things to click with different pictures on them. Ultimately it is extremely boring.