Man, I once trekked a mile down to the nearest petrol station at 10 o'clock at night in horizontal rain that left me soaked to the skin in seconds, with my very last 50p in cash, in order to purchase 1 SINGLE CHOCOLATE BAR.
This, after having turned the house upside down in search of even one bit of leftover dark cocoa powder for baking to spoon straight from the jar or basically ANYTHING vaguely chocolate-flavoured. This, despite the fact that I'd only have had to wait till the morning to have a) a full bank account after payday and b) a perfectly dry weather forecast.
Oh, and instead of taking that chocolate bar home to enjoy properly alongside a nice cup of tea or coffee to make it worth the trouble, I devoured it within 10 secs flat outside the kiosk with water streaming down my face.
... If that's not 'addictive' behaviour then I dunno what is.
The problem isn't the pharmacology of any given thing, but your reliance on that thing to feel good.