The spread of hostels around the world in the last decade or so is a social phenomenon maybe second only to the rise of smart-phones in the current millennium. In fact they could easily be seen as an ideological counterpart to social media, i.e. a residential counterpart, sharing physical spaces, not just baby pics and stupid pet tricks on Facebook.
Modern backpackers' hostels have come a long way from the sometimes-dreary and institutional 'youth' hostels of yesteryear, with their curfews and age limits and nondescript barracks. The modern versions are as varied and diverse as any 'boutique' hotel or B&B, and if the low prices and bunk beds are the lowest common denominator of the genre, then the social nature is the highest, for here you can meet people from all over the world, and maybe even a few locals, too.