Why aren't we seeing more Backyard Cottages?

In a city where the land use policy discussions are centered around density, the lack of new housing units, affordability even rent control and sustainability, why aren't Backyard Cottages more popular and more prevalent?  

On Thursday, I'll be on a panel discussing the state of Seattle's Backyard Cottages with City Council from 12-1 pm.   The premise of the 'Lunch and Learn' is one, to assess the status of current planning efforts and two, look at some alternative strategies from Portland.  

--Matt

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