Craft beer availability is the biggest argument in favour of urban density? Really???
As jje points out, it extends to most products. Beer is a great example because it's not hard to find 'locally' produced beer while it might be harder to find locally produced cheddar cheese, etc.
There's obviously independent places being run in the suburbs, but it's nowhere near the amount you find in more densely populated areas.
In Mississauga, for example, you can only find non-franchise non-chain establishments on a regular basis in the Port Credit, Hurontario-Dundas, and Streetsville. All those areas are pedestrian friendly and appropriately serviced by transit for the most part, they have also historically had higher density than most of Mississauga.
Most independent businesses in Mississauga are run down budget places appealing to minorities that are looking for something the North American mainstream hasn't mastered yet. That's a stark contrast to the sorts of successful independent businesses that pop up in denser pedestrian friendly neighbourhoods. Show me a suburban equivalent to Pizzeria Libretto, Arepa Cafe, or L'Espresso.
Likewise, show me independent furniture places in a suburban setting that compare to the many you find on King East. Or antique book shops. The only ones I ever encountered while I lived in Mississauga were in, that's right, Port Credit.
Anywhere I've lived or visited (I've lived in Caracas, Santiago, Miami, Toronto and Mississauga - visited Washington DC, New York, Buenos Aires, London, Paris, etc) the phenomenon is the same. The more suburban/lower density an area turns, the less variety of product availability and successful independent businesses there are. Jane Jacobs made these observations way before I did, mind you.