Because you're a lightweight
My brother and his lovely wife came round last night. I drank three bottles of wine, and the other three drank 12 cans of Blackthorn, a litre of vodka and a litre of Jager between them. Me and my good fellow were both fine this morning.
By fine, what I actually mean is our heads were banging like a Scouse hooker down Merseyside docks, we'd forgotten our own names and all of our internal organs had melted. I'm still in my pyjamas eating Hula Hoops and wondering why my liver is crying.