Hasn't always been that way. Of course, I'm thinking from the perspective of someone originally from small-town northern Ontario. It used to be that for the most part, the only beers available were from the big national breweries (i.e. Labatt, Molson, and Carling) or maybe a local one, if there was one nearby. In fact, up until 1992, the only draft beer you could buy in northern Ontario came from Northern Breweries - they were legally shielded from competition. (And since Northern Ale tasted like horse piss, you were still basically left with a choice Labatt's or Molson's products.)
Even at the time I moved to southern Ontario for university, the choices amounted to the big national breweries and the smaller local ones, which were rather ironically named "microbreweries," since they were actually fairly large, and as yet there was little to no "craft brewery" industry to speak of.
I imagine that the possibility of selling craft beer to a wider market is primarily due to more efficient production and shipping techniques that weren't in existence 30 years ago.