Before the global assault on beer drinking by anti-alcohol campaigners, the regular ales used in most cultures tended to be 5.5-8.0% ABV, sometimes stronger.  At this intensity a brewer to show off their skills to consumers seeking fuller flavours. 

Such ‘sampling strength’ beers have seen impressive growth during the beer revival of the last twenty years, though no longer drunk from large glasses.  The nature of these beers nowadays is determined by a complex interplay between European heritage styles, new North American trends, and the efforts of consumer groups, beer writers and social media to spread knowledge about what is out there. 

See also: Extra Stout, Sahti