Dark beers

Is there a reason why it seems dark beers are underrepresented in Seattle taps? With so many great breweries and such dreary weather you'd think a heavy dark beer would be found on every corner, but it's usually six kinds of IPA, two European lights, and if you want something darker than Kolsch, it's coming from a can. Sometimes I'm lucky to even have a brown ale. Do darks not sell? Do they go bad faster? Tap operators weigh in please, and if anyone knows a casual place to sample a couple darker varieties please let us know.