Sometimes they are destinations. Drydock in Aurora CO is a great example. Horrible location, but doing very well.
In my hometown (Grand Junction, CO) I've seen a few good breweries with bad locations do poorly, and some awful breweries with good locations do very well.
In some ways, I think Colorado has reached a point of super saturation where it is hard to draw parallels to other markets that are still developing. There are a few other places like this that come to mind as well.
I remember last Christmas taking my family to visit with my folks back in Loveland, my Dad and I decided we would do a 12 breweries of Christmas tour. We hit 15 breweries and we didn't travel further than 35 miles out of Loveland.
And there were a couple of breweries that without a taproom, I'm not sure they would be in business. There was one in particular in Loveland that was serving the most disgusting beer but folks were in line, filling up growlers, and enjoying the place. Another good example is Grimm Brothers, they are in an industrial park sort of setting, but the taproom always seems to be hopping.
Our tasting room is an integral part of our business plan. We are located far enough from downtown so that bars won't feel competitive pressure from our operation but close enough that people won't have to drive very far to visit us. Far enough that rent is cheaper, but close enough to use municipal transportation, etc.