I would wager that the ‘answer’ is: brewed because they are so popular (with craft beer drinkers). A hoppy beer like an IPA is often an ‘acquired taste’ because it is such a flavorful beer. For somebody that is a BMC type drinker, an IPA is an ‘overwhelming’ beer. I don’t think that craft breweries/brewpubs would make so many IPAs if there wasn’t a demand for them. I homebrew a lot of different types of beers and I bring a variety of those beers to parties; recently brought a case to a Memorial Day Barbeque Party. The number one question/comment I get is: “Is such and such beer hoppy? I don’t like hoppy beers”. At this recent party the Oatmeal Stouts went quickly. I came home with 3 bottles of IPA. I was obviously at a party that was populated with folks who are more ‘mainstream’ and not BA type folks. Cheers!