Americans by and large are vastly more anal than most Brits and strange as it may be. they seem to derive loads of fun from patterning everything. This article isn't deadly dull though and does explain pretty well why so many sporting clays shooters gravitate to ½ choke for almost everything: http://www.shootingtimes.com/2010/09/23/longgun_reviews_st_headintheclouds_201002/