It's hard to blame breweries for responding to customer demand. When I show sales reports to brewery reps and they see that 14 (or more) of the top 25 selling year-round beers are IPAs, Black IPAs, and DIPAs they'd be foolish not to try and get in on that action.
There seems to be a very small, yet exceedingly vocal (thanks in large part to BA and RB) crowd of geeks demanding ever-hoppier IPAs, massive imperial stouts, and enamel-destroying sour beers, and for better or worse breweries respond to what they see as the "hot styles" based on the various top 10/50/100 lists.
Thankfully, the pendulum seems to slowly be swinging back the other way, at least here in Portland. I'm not sure if it's due to the more "mature" nature of the good beer scene out here, or simply a backlash against the ubiquitous IPAs, but more and more people are asking me for suggestions for lagers/pilsners on a daily basis. The local breweries seem to be picking up on this trend quickly, as evidenced by the fact that Ft George released their lager as one of their initial canned offerings, HUB is going to be releasing their lager in cans soon, and Heater Allen is selling bottles as fast as he can fill them.
All of that said, I've never had a problem finding a well made stout, porter, sour ale, or other style of beer when the mood strikes.